Slinger

I took a 2004 4.2L S4 for a short test drive yesterday and it ran and drove great. It has 125K on the odometer, but had all of the problematic timing chain hardware replaced 4K ago and the price is right, so I decided to buy it. I filled out all the paperwork and paid for it. I had to do a little running around to get a t-plate and fill the tank before I made the 2 hour trip home.
During this time it developed a misfire, then the CEL came on intermittently flashing and solid, then the yellow oil can light came on in the message screen followed shortly by the red oil can light. I stopped and checked the oil, which was full, as it was before my test drive. When I started it back up, there were no lights and it was firing on all 8 again, but not for long.
I got it back to the seller's shop and his code reader showed a misfire on cylinder 2. He replaced the plug and the coil. When he started it again, it was firing on all 8 and didn't have any warning lights on. We let it idle for 10 minutes or so, then took it back out on the road. We got on the interstate and drove for 10 or 15 minutes without any trouble, but then it started missing again, seemingly just on 1 cylinder (he didn't bring his code reader with us), then the CEL started acting up as before, then pretty soon the yellow oil light, then the red one, as before. Shut it off and restarted it after waiting 5 minutes or so 3 or 4 times, and after a little bit it seemed like it was misfiring on more than 1 cylinder. We parked it to get hauled back to his shop.
The seller had already deposited my payment, and couldn't do anything about it at this time because the banks were closed...Saturday afternoon.
I'm probably foolish for not just jumping out of the deal right then and there, but the car is very nice and the price is right, provided this problem is taken care of. He says he'll find out what the problem is and fix it. So...it's in limbo until I hear from him what's going on with it.
What I'd like to hear from any of you S4 owners who have insight or similar experiences, is what this problem could be. How are the misfire and the oil pressure lights connected? Could it be a minor problem that can be relatively easily taken care of, or if it's a sign of bigger problems to come.
Should I keep my fingers crossed, or bail?