I have an 88 TE (wifes kid hauler, 165k). We love the ride. It is very solid on the highway.
The big $ items that will most likely need replacement are:
A/C evaporator $2k
head gasket $1k
water pump $600
My car has a leather interior which is showing it's age. I would rather have the MB tex. Look for a car with a good maint. history, preferably one with the above items already replaced. The 103 straight six is easier to work on than the 104, but has less power.
I drove 300+ miles through Kansas on a bus. trip in a 2003 Buick Century rental this past week. I was wishing I was in the TE the whole time.