Newbie question;How do I replace a 32bit version of 11.1 with a 64bit version of 11.2 or is it even possible?
It is possible. Just upgrade! Be sure to back up your data anyway. (In fact, I did it on one of my machines at the office).
Backup, wipe clean - if you have to ask how to do it you don’t know enough to be able to know which redundant files should be removed.
Just a friendly suggestion.