It's a fair price for a car as you describe, but IMHO it not a screaming bargain.

I'm not intimately familiar with the 190D 2.2 but the transmission harshness is most likely a vacuum control problem. The cruise control rarely works for more than 10 years, usual cause is the cruise control amplifier ($200-300) but other things can break as well. Check the brake light bulbs - if the bulbs are burned out the cruise will not work. The coolant leak could be anything - the fuel is heated by engine coolant but coolant leaks from that system are not common. Water pump or hoses are more likely causes for coolant leaks.

If the thought of dropping a $1000 to perform repairs on this car makes you feel a bit queasy I think you had better reconsider the whole deal - your candidate car is 22 years old. Old cars break and if you have to pay somebody to do the diagnosis and repair work $1000 is a pretty easy figure to exceed even on seemingly modest repair jobs.

On the plus side if you can put up with the slow acceleration I'd expect you could get 40+ MPG on the highway from your car. Zero rust is a big plus - most W201's north of the mason-dixon line have rust issues at this age.

I had an 86 190D with a 5 speed transmission that would deliver 42-44 MPG on the highway. Many people don't like the W201 body style but I'd buy one again in a second. Good luck.