The car is 14 years old. If it was maintained by a mercedes dealer its a good bet that the previous owner didn't want to pay to have certain things fixed because of the cost to car age ratio You on the other hand are a little more thorough because its your son.
Right now on my car I need an abs sensor, front rotors and I need to replace the steering shock, I haven't gotten round to it yet. But if my daughter was old enough to drive it (she's 11 months old right now ) I would fix that stuff immediately.