GingerBREAK is an .apk to root the Optimus V among other devices, not to be confused with Gingerbread (Android 2.3)
[26.04.2011][v1.2] GingerBreak APK (root for GingerBread) - xda-developers
After that, I would suggest installing ROM Manager from the app market, and from there install a recovery (either xionia recovery image for flashing Harmonia Froyo 2.2 based ROM, or clockworkmod recovery image for flashing IHO/BACKside CM7.1 (Gingerbread 2.3 based ROM).
To summarize:
1. GingerBREAK to root the phone
2. ROM Manager to flash a recovery image (xionia or clockworkmod)
3. In recovery mode, wipe data, cache, dalvik cache, format /system, /data...etc.
4. Flash custom ROM in recovery mode (recommend Harmonia or IHO/BACKside)