Jenn,
I haven't left nursing for more than a couple of months yet but I can absolutely tell you that I am SURE that I would have a hard time returning after a number of years off. You just lose so much of that stuff when you aren't doing it every day. I even find now that areas that I am not exposed to frequently start to get fuzzy and I have to read up on them. Give yourself some time and just keeping asking questions. I personally find it helpful to read materials so maybe you can find a current journal (AORN) or textbook that would refresh your memory?
Good luck!