Wow, working for 8 yrs in research, eh? That's pretty cool. My Sis is a PhD in Biology (she has a specialty but I can't understand it OR pronounce it) after having started her journey as a BSN nurse. She's lost funding for her lab work and is facing the prospect of going back into the hospital and doing 'nursing' again. Pretty intimidating.
Anyhow, I 'spose you must be dealing with alot of uncertainties. I'd love to have someone with your 'skill set' come to my unit and be your mentor. I bet the skills you've learned in THINKING CRITICALLY would be wonderful and helpful. So have some confidence--I bet you'll do fine.
The hours and scheduling issues are kind of a boogey-man. They are complained about and worried over--but hundreds of jobs require nightshift workers and weekend/holiday staffing. It's not just nurses. And hundreds of thousands of nurses find some way to have a life inside our schedules.
How do you get into 'Critical Care'? (Think critically here; start at the beginning and get to the end by way of the middle.)
I 'spose that you've gotten the basics outa the way? BLS and license? I'd advise you to apply for a job in a 'step-down' or 'telemetry' unit. Much like Med-Surg but with heart monitors. Get your arrhythmia training and your ACLS. Put in a few months there and then begin volunteering to 'float' to the ICU/CCU when that opportunity comes along. Then sign up for an overtime shift or two there. (Believe me, the opportunity WILL come along.)
If you like it (as you think you will) and the folks there get to know you--you will hear 'thru the grapevine' when there'll be an opening and have a cadre of ICU/CCU nurses that have worked with you to tell the Manager that you've been there and worked well with them.
Good luck. If you love a challenge and love a job that requires you to constantly use your brain--critical care prob'ly will suit you.