Are you sure the rust isn't just surface rust? If only surface rust than some cleaning and grease would be best. Do NOT have the car painted, it will kill the resale (unless just some touch up at that area only). I would NOT buy a repainted car myself unless it was but a few grand or so (junker). My 98' C280 has no paint work on any metal surfaces, I paid a premium because of it.

Please post a pic so we know how much rust and how bad it is.