The one that bent the valves - was it a '95?? I bet it was. They had a bad run in '95 with that problem.
http://www.markviii.org/htdocs/dc/dcboard.php
The above website is very valuable for these cars.
With the mileage, you should be paying no more than $1500 for the car.
These cars are a blast to drive if they are right. I bought my '93 back in January. I paid $2000. Keep in mind that I had wanted one since I first saw them. She was asking $3200. I started categorizing what it would need. I offered the $2000 and she said she would think on it. She called back an hour later and said ok. I have done the following:
1 - The climate control buttons were thin and crack on this car. I replaced the climate control panel with one from a '95. The buttons are made better.
2 - The air suspension is wonderful when it is right. It can be expensive to work on. My front struts were siezed. The struts are integral with the bags up front. I replaced my whole air bag setup front and rear with a mMonroe conversion kit. The kit cost $500.00.
3 - As I said, you WILL replace that tranny. That slipping out of gear and back in is likely the MLPS sensor. That is a $30 replacement from Autozone. - Look under Neutral Safety Switch. The old type were not as watertight as they should have been. Corrosion gets in there and then the tranny will do weird stuff like that. If the tranny is ok otherwise, do the following as soon as possible after getting the car. Pull the tranny pan. Pull the valve body. Replace the 1-2 accumulator piston and springs. The old type break and lodge causing failure. Do what is called a J-Mod. (the 1-2 accumulator is part of this) It increases flow and reduces slip as the tranny transitions from one gear to another. Go to the MarkVIII site and search for J-mod. Install an Auxilary cooler. Flush all the old fluid from everything. Replace with Mercon V.
4 - The radio amplifiers tend to go bad on both the premium and the JBL sound systems. To put in an aftermarket radio, it is best to run new speaker wires and new speakers as well. The factory speakers are very high impedance. The wires going to them are VERY thin. It was a good factory setup, but you can put better in there now for often less than you can find a new factory amp.
5 - Cruise Control. Mine was disabled by the Ford dealer when I bought it. These are under a recall. There is a switch plumbed into the brake system. If the membrane between the electrical and hydraulic side of that switch goes bad, a fire can result - sometimes hours after the vehicle has been parked. Ford will look at the vehicle, replace the switch if needed, and put in a new harness that will disrupt electricity to the switch if it goes bad.
I have no regrets about mine. It is a comfortable car that also handles decently, brakes decently, and will get down the road with all haste.
The guys over at the Mark VIII site are good guys. You will get a lot of support. Just realize that a Mark VIII is not a buy it and run it and forget about it car. It will demand love from you. If you treat her right, you will be happy.