The shop owner is going to want the diagnostic charge in the very least, but if it's been there forever he might accept half of it.
He's going to have to go through a "mechanic's lien" in order to get it such that he can legally sell it but then you won't have a title.
Try to get him to contact the owner and get the title, not having one makes it a hassle in most every state. I once bought a car that way and I had to step through all sorts of hoops to get it legally back on the road after I replaced a simple rocker arm stud. Around here that involves the DMV (Department of Motor Vehicles) to send out a registered letter to the last previous owner on record as well as checking for any liens and give them 30 days to reply, after no replies (or we don't want it replies) then they'll issue you a new title with all the paperwork. Simple matter of getting a proper title from there, insurance and then you can get a tag.
Makes sense and it's only for your protection, if you buy something without a title the PO can still report is as stolen or may have already thus if you're caught with it then it's put into impound and a war begins. Only paid $200 for the car, $1 for the part (valve cover gasket was reusable) and in about an hour's worth of time it was a totally clean driver that ran well. If I recall I ended up selling it for $650 so, considering labor time and all the tag & insurance hassles I probably did nothing more than break even. I bought it on the premise of a car for my previous girlfriend's son but he didn't have the money to even kick in the $100 I wanted as a down payment on it. Told him I wasn't going to give the thing away after what I had invested in it so he eventually talked someone from one of the Tribes into giving him an old Ford Taurus that was not only on its last leg but had an expired tag and no insurance. He drove it that way for quite a while, if I recall the car gave up long before he was caught for the expired tag. Had he been caught they would have towed it anyway, an expired tag isn't so bad around here but no insurance not only puts the car into jail but also you.
Our backwards state finally figured out a way to check to see if you've got insurance just by your tag #, too many people were forging insurance cards. I sure wish they had that system in place when a guy virtually totaled my Pace Car but after it happened he pushed his badly injured girlfriend behind the wheel of his truck. Once she was semi-recovered at the hospital they came and wrote her 14 tickets. There were already warrants out for his arrest for no DL and driving without insurance but I'm sure they caught up with him over time. Too late for me, if the sucker had been legal my $30K Pace Car (+$5K worth of mods) would have been repaired instead of now in storage so the only bright side was that I got my '96 GTP at auction for around $4K. Not a 12.9 second 1/4 mile car by any means but plenty fast enough and the handling, considering it was one of the 3,704 that had the Corvette suspension, sort of makes up for that. In time the Pace Car will be restored but I figure it's going to cost around $6K to do it.
