Do a back up in cwm before you flash anything.
Yes, what he said, gosh, it's been so long since I rooted mine.
And I also do a nandroid backup in cwm before each wipe and flash.
And depending on where you get the ROM, the instructions usually advise you to:
Backup,
Wipe data (factory reset) when changing base builds and usually just cache and dalvik when just upgrading build versions.
Example: Starting from stock you will want to run the All in One to gain root and install cwm.
Now you can perform a nandroid backup of your original OS.
The only trick here is in order to access the recovery mode, you will need either ROM toolbox or Titanium Backup to navigate to the option for reeboot into recovery.
Any how, I'm sure you have come across the wealth of posts here and elsewhere regarding the rooting and flashing of this fine device.
Have fun, and Flash Responsibly. Your relationship may depend on it..