It seems you've all but bought this car. I agree with Damlier on price and getting it inspected. If you're ready to buy this car I would get it inspected and then go back to them with the list of things wrong and have them adjust the price accordingly.
Are there any records with the car? That would help confirm what has been with the car.
Another thing you might want to do is get the vin # and head over the the local benz dealer. They can type in the number and tell you what has been done at the dealership over the years. If you're real lucky you might be able to find out the previous owner name and he can tell the real story on the car and perhaps he may have some of the service records available.
From the pics it looks pretty nice and it has my favourite coloured interior - palamino tan. Easier to keep cool and not as somber as the dark interiors. I've got a cream one myself.
Apart from the gas mileage and being a bit cumbersome to drive around town (it is a big car you know) I can't really flaw these cars. I love mine