Can I still do part 2 after abandoning/not completing part 1?

I have the same problem as another post where Sir BillyBob seems to be invisible. I tried using a gamesave editor to drop in true seeing scrolls, etc. He never became visible. I even pulled in a Vampiric mist spell and it didn't seem to affect him at all. (All but my PC eventually exploded just standing in it, he never failed a save)

I think I've done everything I can find - and certainly have gone to every area already.

More importantly I have previously completed part 1 in an earlier attempt at running through the game. In probably late 2007 early 2008. Long story short, that was my first attempt to finally finish all the original games along with a bunch of mods. I upgraded my mobo and lost the install. This is on a laptop where I won't have that problem. So if I were to skip out I don't think I'd be missing anything unless stuff has been actually added since then.