If you look at a car as the sum of all parts (repair risk), your estimate is too low. There are plenty of text telling one how much to expect to pay per year. If you were to spend your time here and your money appropriately, you will cut the consumer's report figures by 75%, even if you pay someone else to do the work.
Your real risk in that car is the A/C. Does it do good now!? Is there a history of repair? In your area it is real easy to spend a couple g's on A/C.
Bosch Master, ASE Master, L1
33 years MB technician