97 GTP Transmission problems

I have a 1997 GTP and I am worried the tranny may go out, but I am not 100% on it. I ease into the gas it isn't as bad, but if I all of a sudden lay into it, it has a tendency to slip. Sometimes it will do it real hard, and it feels real jerky. It likes to do it on hills too, and I can be going 55 and if I lay into it too much the car will shut off while I am driving. Does this sound like the transmission is going out? And if so is there a way to snag one for a super cheap price? I am not made of money. Thank you.

Sounds more like it's ignition related. Which is extremely common. When was the last tune up.

Spark plugs
Plug wires
Clean throttle body
Clean maf
clean air filter