Automatic Transmission problems of the 1996 Buick Lesabre

I was driving back home from a friends house and had the car parked in my drive way and it was left running and it was in park then I went out to leave and the car was running for about 3 min sitting there and I put it into reverse and it would not move no matter what so I tried all the gears it wouldn't work so I shut off the car let it sit for about 5 min and started it up then put it into reverse again and it did then I drove about 50-100 ft and it felt like it was slipping and then just the other day I went out to start it and it was still in park and it sounds like a powersteering pump with no fluid and it sounds like a big nest of bees and I checked the fluid level and the fluid was burnt and there was debris in the fluid so the car don't work. So my family had to go buy a new car when we are broke and now I have no way to get to work. There was nothing done to resolve the failure yet im going to go buy a new transmission.