Dude, that sucks. I know how much you like(d) your car...
I feel the same, however. I've got 110,300 miles on mine now and am concerned about how long it will go. Right now, the only issues I've got is the seat heater on the driver's side is not working and the turn signal on occasion goes bonkers (luckily, not recently, however). But, I have a list saved on my computer all of the repairs that I have had to have done on this car in the past 4 yrs/46K miles. They include 2 water pumps, 2 ignition towers???, rack/pinion assembly, front struts, both front seat motors (driver's side went out, passenger side...the frame broke), Intake Manifold repair (I got my money from the GM class-action lawsuit finally for that one), fuel gauge (would flop from E to F and back again...all the time), 2 transmission services to try to find the source of some occasional slippage (which was never found). Now my 80K tires (with only 35K on them) are worn out and even though Sears told me I'll get a lot discounted for the pro-rating thing, I still will have to shell out a sizeable chunk of money toward new tires...and Sears still (after 4 trips to their shop) can't get the front-end to stay aligned.
The problem is that the car is paid for, my wife may lose her job with the schools at the end of this school year (in June) and I don't have enough money to buy another car. And...I like this car...and I'm addicted to the HUD

. So...I continue to change the oil every 3,000 miles and take it to my mechanic at the first sign of a problem so as to avoid even higher repair bills.
The whole reason that I got my Park Avenue when I did was because my 1995 Roadmaster was similar to your Park Avenue, in that it would cost about $3,000 to fix all the problems with it and I did not have the money to pay out...but was able to afford monthly payments on another car. So I've been where you are. And I must say that there are a lot of times that I wish I would have tried to get the money together to get that Roadmaster fixed, instead of getting rid of it. I miss that car a lot. I most definitely would consider another one.
I agree with the others in that it would make a lot of sense to trade out of your Park Avenue...but if you really want to have a Park Avenue, perhaps look for another.
Good luck in whichever way you go with this. Our Park Avenues truly are fine cars, but it seems GM's practices have plagued the Parks with some hit/miss reliability. Let us know what you decide to do.