^good work! Perhaps you and the seller can come to agreeable terms and it will be yours.
You can do the DIY rebuild...I did (fully documented here
http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/492267-jacobs-rebuild-thread.html)
I'm happy to share experiences (PM me and I'll give my phone# if you would like to chat)
I had deja vu when I read your posts. This car sounds a lot like mine was when I bought it, and your expectations of what it might need were also very much like my own (under estimated). This thing cost me more $ than I could have possibly imagined, but it wasn't a burden financially and I have no regrets. I can't put a price tag on the experiences I've had because I bought my 930.
I think the important thing is to manage expectations, and to "know yourself" No doubt you can drive these cars even though they have issues. I drove mine with busted piston rings and melty piston (one of the photos above). To from the Carolinas twice...one of those times was for a track day. It was still the fastest car I had ever driven, despite the engine issues. Once I knew it had those issues for sure, I
had to fix them properly...that's me. Once the engine is dialed in perfectly, are you really going to drive around on 30 year old suspension bushings that are shot to hell? Not me...so new suspension followed shortly behind engine.
^this is the slippery slope by the way (if you haven't heard of it before
)