I have just started messing with this stuff so I am no expert.

You can try out different roms without losing your current data. For me to install a custom rom I had to install clockwork mod recovery and with that you can make a backup image that you can just restore if you don't like the new rom.

You can also use titanium backup plus to back up applications and or application settings. I used that to keep some game saves that I restored to the new rom after re-installing the game.