going cheap might hurt...
I think this is one of those headaches that needs to be addressed by a reputable expert. Somebody that will be held accountable for a job well done or not (and keep at it until it is). With possible window removal (to get it done properly), paint matching and rust mitigation so that there's no issue in the future, I'd be surprised if it can be done for less than a grand. I've never been able to get body and paint work done properly for less than a grand even for a small area. Maybe I spent too much, but I never had an issue after the work was completed.