I have learned, over the years, not to try to finish some else's project. Even if it has a ton of great parts and seems like a good deal. Too many times you end up with a bunch of hidden problems, or a whole rig that was done poorly.
With that said, if everything is really done, and all it needs is wiring and the interior installed, then thats not a whole lot. Wiring can be a hell of a job though, and if you don't know what you are doing, then it can be hopeless at times. Also, the seller claims that it runs perfectly once its wired, but there is no real way to prove that, and if you get it wired up and it runs like crap or doesn't run at all, there is not much you can do. You are basically buying a ton of parts with the hopes that you can get it running without much more invested.