OK, some definitions:
Baseband is the driver that runs your physical radio antenna, the one that gets your cell service. That has 3 versions, all of which work on your phone. You're currently on ZVJ (which displays on your phone and mine as MVJ), which means that in order to properly root, you MUST revert to ZVD first. The instructions are right there in the thread that I linked to, and it is not an option. Do not worry, you can upgrade again after you've rooted, just make sure that if you intend to do so (it is not necessary) that you do it BEFORE you install a custom recovery.
The software you're using is another matter, and your service will depend on you having a matching ROM software and baseband architecture. If the ROM is built for ZVD and you have ZVJ, you have to patch the ROM before you'll get service. That's OK, it doesn't hurt anything, so I wouldn't worry about that right now. You'll get comfortable with it. Just follow the posted instructions and it'll work. Trust us, we've all done this... some of us like... a million times.