1986 Volvo 240 DL With Electrical Problems

Help! I could really use some advice. I have a 1986 Volvo 240 DL which seems to be losing its electrical functions one by one. When I bought the car two years ago the radio didn't work...no big deal. Now its the power windows, brake lights, and rear window defroster. Every once in a blue moon either the radio or the windows will work for an hour or so. So far, I still have blinkers and headlights, but believe me, as I drive home on dark, rural roads at night, the thought of losing the headlights is never far from my mind. I don't know anything about cars, but it seems to me all of these things are connected somehow. The question is... is this an expensive problem to fix? I REALLY hate to sink money into a car that is this old with 322,000 miles on it. But, I'm not in the position to buy a new car (or even a decent used one) at this point in time.

Also... I've noticed that the car doesn't like to reverse SLOWLY anymore.
It doesn't want to move unless I really step on the gas hard, which is not exactly a great way to back out of a parking space at a busy grocery store! Is this an indication that the transmission is dying?

Any and all advice is very much appreciated! Karen