Hello all, I'm hoping ya'll can help me as I need this car to get me to start a new job tomorrow.

my '90 240 with 220k (auto transmission) will not come out of Drive. I was driving it home tonight and pulled over to get gas. When I went to put the car into "Park" the gear shifter just slid through the gears. I can hear a few clicks but it does not actually change gears.The button on the top of the shifter will pop in and out on a few of the "clicks" but again this makes no difference as the car just stays in "Drive", idling. So the only way to keep the car from driving is to shut it off and put on the E-brake. Transmission fluid level seems to be fine. It literally will not engage "Park" or any other gear at all. As soon as I start the car it tries to drive. Please tell me there is an easy way to fix this! I've got to start this new job tomorrow!

Pertinent Info: the transmission is not the original transmission, it was a used transmission put in approximately 50-60k miles ago. Also, the car has been overheating when sitting in traffic lately. Not 100% sure yet if its the fan clutch or the thermostat or something worse, but I mention the overheating problem in case it might have to do with the tranny problem.