7 grand? IMHO, no it's not worth it.
You really have to do your homework on these cars and make sure you check the car top to bottom before purchasing it.
And if you are going to opt for going out of warranty, then you better know or be willing to learn how to DIY.
2008 E92 M3: Sparkling Graphite | Bamboo Beige | 6MT | CF Roof | HRE | Eisenmann | BPM Sport | Swift | Arkym | M-Performance