This would be useful to me also, as my front bumper has a nice car park scuff and a could of dents.
I hope your mate is paying you for the damage regardless or he isn't exactly a mate
I wouldn't be so forgiving, you will need transport regardless and if he made your car unsellable why should he get away with it ?
If i did it to a mates car i'd pay up regardless if they wanted money or not as it's the right thing to do and i would expect the same in return
If the car is a shitter, then do the job yourself. The doors will be available from scrapyards (although dents can be pulled easily enough). You can rent a dent pulling kit and do that yourself too.
If it's metallic though, you're probably screwed.