In all fairness, a LOT of M3s bumper/fender seams are off. Someone started a thread about it and there were a number of other replies that confirmed they had the issue as well. Scratches into the color coat will require paint or touch up. Depending on the shop it may have been cheaper to paint than touch it up. The oil leak is an issue though. Could be easy, could be a real issue. It IS possible they didn't know about the leak. The paint they're not legally obligated to disclose. You'd be surprised to know how many cars get repaired at the dealership that owners have no clue about.
Now, don't take this as me being overly critical or second guessing your decision, just some hopefully helpful info to use in your continuing search. Given everything combined I'd probably have backed out as well.
I'll keep my eyes peeled and let you know if I see a good car for you.
Any specifics you want or don't want?