First off to get Rev. A and GPS/agps you have to update your rom radio to 3.xx.xx Before you would have to upgrade and flash a custom rom for verizon.. but as of a few days ago theres a leaked VZW upgrade floating around in this forum.. You could try installing that... it should enable gps.. maybe agps (I havent tired it..) Or you could go the root of unlocking your phone and flashing a custom rom, theres plenty of nice roms floating around this forum too.
As for backing everything up... You could downgrade the radio but why would you want to? :P Before you do any flashing backup everything.. a good app is Pim backup(google) its' free.
Sorry if this post isn't that informative... hopefully this thread will be:
http://www.ppchaven.com/viewtopic.php?f=63&t=4 you'll have to register to view it..
Also after you upgrade your radio you gotta do this aGPS fix for vzw to get quick locks:
http://wiki.xda-developers.com/index...VerizonAGPSFix
edit: Did you try using BTPan w/ ICS?