Most of these suggestions seem to gravitate towards you going to nursing school. I will be the voice that says no you definitely should not, but there are valid reasons for that.
1. More than likely you have decades of experience in another field and also likely that you are making as high or higher salary in that field than a new RN will make, and your retirement/benefits are vetted. Should you leave for RN school you will be putting 7+ more years of work (at least 2 for school and 5 to get vetted for retirement in another job). This point is moot if your IRA is well-funded and/or you are already wealthy from other means. This is on top of the time to actually get thru RN school so if you are seeking benefits/retirement from an RN job you won't be able to draw on them until at least 75.
2. You will face ageism. You will likely be 67+ by the time you graduate nursing school and thus would be able to draw social security and be able to retire anytime. Employers will be extremely hesitant to hire someone who they might feel is a liability as you will be able to suddenly retire whenever you want to. You might not want to retire yet or at all, but employers will think of these things making your first job as an RN very difficult, far more so than usual for a new grad. Regardless if you are as healthy as someone half your age or not, these will be concerns for someone in an HR office somewhere who you will never meet and they will never meet you except your resume and application. They will have concerns like these, but might rationalize these concerns as other things to avoid the appearance of ageism but do not think that these types of concerns aren't being considered by all of your potential employers. They'd see you high school graduation date and decades of experience and be able to piece this together, they don't even need to know your exact birthdate.
3. Costs of school. There are more costs to school than simply the money and time. You will face mental and emotional challenges that you may not be prepared for. As mentioned in point 1, you most likely have decades of experience in another field and thus would be used to a certain level of mental/physical exertion from that career. RN school is rife with challenges that many people your age are simply unwilling to face as at that point in their lives they desire the well-earned comforts of retirement and not the hectic challenge of schooling right before retirement. Nursing school instructors will not take it easy on you because of your age and you will be expected to keep up with students half your age or younger. This means being able to lift heavy patient/objects and being on your feet for 10+ hours with little opportunities for rest and possibly being at a fast walk/slow run the majority of that time. Do you think you can physically handle that? Sure in many SOP's it's said you can simply go get a lift assist device. In actuality those aren't used much and you will be expected to move heavy patients by yourself or with 1-2 other people. Can you imagine yourself and 1 other person lifting a 200 pound person deadweight from a bed to chair or vice versa? Do you want to spend 8-10 hours a day at school and then study for 1-3 hours after that each day? Do you want to be full of stress and anxiety right before you reach retirement age and constantly be stressing about the next test or some assignment? These are the types of questions you need to ask, and I advise talking to the school counselors at programs you are interested in to get a glimpse of what to expect and then evaluate yourself if you want to go thru that.
4. Time is against you. Evaluate why you want to go and try to modify your plans accordingly. If your plan is to treat patients and/or try to do good for others than going to LVN school may be better as it's cheaper and quicker than RN school. You will be able to get out there working quicker and thus be able to have at least a few years of work before you hit retirement age. RN school usually requires some prerequisites in addition to the 2-4 years required to complete the curriculum. That means if you are 63 now you most likely won't be a new-grad looking for work until you are 67-68. How many years of your life do you expect to be working? As mentioned, you must begine drawing social security within a few years of that and you'd be eligible for retirement during nursing school. You are trying to maneuver yourself into disappointment by going thru such a long program that close to retirement. I seriously advise you to consider LVN instead if you are dead-set on becoming a nurse as the program is far quicker at usually less than a year with little/no prerequisites.
5. What is the reason for the sudden career change? If you simply want the letters "RN" behind your name then definitely do not do it. If you simply want to become an RN to fulfill a life goal, but don't plan on reasonably using such license then go ahead. If you want to get that license to try and get more money for retirement then you will fail. You will have lost opportunity costs from the years of school. Assuming average US income of 40k/year and your schooling takes you 5 years you would have lost out on 200k on income you could have gotten from your previous job. Assuming the average income for a RN of 70k, that is a 30k boost, but you'd then have to make up for that initial 200k lost income, AND THEN add the actual costs of schooling on top of that. I won't go further, but suffice to say you will have to work several decades to make up that lost income and increased expenses and that probably isn't what you originally intended. If you simply wanted to go help out somewhere then I suggest volunteering at a hospital. That will take care of any altruism wants of yours and allow you to keep your current income/benefits/retirement.
Sorry to be the dissident one here, but many seem to be advising you from an idealistic point of view. The reality of the situation is that unless you already are wealthy this would be a terrible decision for you to undertake being so close to retirement. If you are already wealthy and simply want a change of pace then think about what I said and then go according to what you decide is correct.