From 11.1-32bit to 11.2-64bit

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.