OP, a picture is indeed worth a thousand words, especially in this case. We could accurately determine if its 2 inch keying or 3 foot or more keying.
If it's the former, it's probably not going to affect resale values. If it's the latter, depending on the work, it could affect resale. Given the plethora of used M3's that we're seeing for sale now, unless it's a true unicorn with everything you're looking for, I'd walk and find another...but that's because I'm super choosy on what garage queen I'm going to worship
