I test drove the car today. It drive very nice with very good tires and brakes on it. There were no warning lights on and everything seemed to be in working order. My only issue was the headlights were really yellow. Also even though it had the Harmon sound system it did not have SAT radio and AUX input. The dealership very much wanted to sell this car and threw every offer they could at me. While I did like the car I'm not sure it's really me.
Since you have not determined this car is really you, some things that could tip your decision in favor. You have nothing to lose, shoot for the moon, the worst that could happen is they say no (No great loss, the car was not really you anyway), the best that could happen they give you everything you request (What the dealer would really be giving you is peace of mind, any major items would be under warranty):
How badly does the dealership want to sell this car?
Is this car being sold as a "Mercedes Benz Certified Vehicle"? If so, all systems service should have been performed. Request copies of all service conducted by the dealer. This should include restoring the headlight lens and tires with at least 75% thread.
Request the dealer provide you a recent CarFax report to ensure the car has not been salvaged or in a major accident.
Request the dealer provide you a 4 year 80,000 mile warranty.
Just my $.02 , You have nothing to loose right? =)