97 Jeep Grand Cherokee Limited Transmission Problems?

[Megan]

I have a 97 Jeep Grand Cherokee Limited 4x4 8 Cyl. And the transmission has about 187000 miles on it. It has been acting like it may be slipping a little bit, but I haven't had any major issues with it until yesterday. As I was driving about 50MPH the engine began revving and all of a sudden my RPM kicked up into about 5. It never does this. I pulled over and started it back up and got on the road, and now my RPMs won't shift gears. I made it home about 5 miles down the road, going 15mph with the RPMs at about 4 or 5. (Which is obviously incredibly high). Is there anything I can do as far as just replacing a part in the transmission, or is it likely the entire tranny is shot? Also- I have to wait for it to heat up to 210 degrees before I can drive it without it cutting off. Somebody please give me some insight as I know nothing about vehicles. Thx