The age limit for enlistment is currently 42, though there has been talk of lowering it to 35. The goarmy.com website actually has 35 as the age for enlistment: Enlisted Soldier | GoArmy.com
. However, you can read the current regulation here: http://www.apd.army.mil/pdffiles/r601_210.pdf
-- age is discussed on page 5, and it says 42. Even though you are an LPN, you would still have to go through basic and AIT (16 weeks of training) -- after all, in the Army we are soldiers first, and you have to learn how to be a soldier. Bear in mind that there is no guarantee you'll even be placed in the MOS (job) that you desire. It depends on the needs of the Army and whether or not they need LPNs at the time you enlist.
You will likely be eligible for the GI bill for further schooling, but there is currently no tuition assistance for the military due to the budget crisis -- it was just taken away last week.
If you come in under the Army Civilian Acquired Skills Program (ACASP), you could come in as a SPC/E-4. Look at page 86-ish or so in that PDF I linked. I do believe that 68WM6 (LPN) is approved for ACASP, but you might need to have LPN experience as well, not just an LPN license.
Have you talked to a recruiter? Might be the best thing to do just to sort out the age question up front.