Hard shift/Odd idle

I have a 2000 Sunfire GT Automatic with 241,9xx KM on it. a couple weeks ago, I jumped in the car to go to work, started it, shifted into reverse and it jolted the car and clunked, I drove backwards outta the parking spot, stopped and threw it in drive, it clunked again and jolted the car. I proceeded to slowly drive the car to work as I was already late and it was only a 5 KM drive, during the whole drive, it shifted really fast and hard through each gear even though I was light on the gas pedal. The check engine light had turned on and the traction control had turned off. by the time I had gotten to work, it started to shift normally and never shifted hard again, and the check engine light turned off and the traction control turned back on... until today. the check engine light had turned on thursday of last week, but nothing was acting out of the ordinary. it was shifting fine, and running fine, aside of another idle issue that I will ask about later. So then again, I went to jump in the car to go to work today, threw it in drive (cuz I had the car parked backwards in the parking spot), and it clunked harder than ever. right after, the traction control turned off. and the cooling fan kicked in and has been running constantly since, now since the check engine light was already on, I'm not sure if that was affected also. its shifting through every gear like its got a shift kit. everytime I shift outta park, it clunks really hard into gear. this time its not easing up either. all day its been shifting like this. I've been being nice to it all day and its not getting better like last time. I really dont wanna drive it like this cuz I dont need the tranny going, but I need my car! I checked into the possibility of adjusting the TV cable, but there isnt one. cant check the fluid level cuz I dont fit under the car on the ground and I dont have anything to evenly lift it.. just wondering if there was a possible sensor that could be causing this. I dont have access to a code scanner either and I'm in between paydays so this is very difficult. I can borrow a little of money, but not enough to make this any easier..

now to the idle problem. the car usually runs at a tick under the halfway mark on the temperature gauge. Once the gauge reaches the quarter mark on the gauge, the idle starts dropping. by the time it hits the tick under halfway, the car is idleing at 500 rpm. it starts to putt and miss and has really poor response if I'm trying to go from a stop sign or red light.

:banghead: good thing I only paid $500 for this thing.....