Need some help upgrading to the GPS ROM

[XxEastside13xX]

Right now im running an outdated custom rom, forgot what its called, but I wanted to upgrade to the new rom to be able to use the GPS. I remember previously reading somewhere that first I had to relock the phone and revert to an old official rom THEN upgrade to the official GPS rom. Can somebody just give me some instructions and programs to download in order to achieve this. Also whats a good data back up tool. I want to back up my contacts and text messages mostly.