Where is the TPS sensor and how hard is it to fix?

The TPS Throttle Position Sensor is not hard to fix. 30-minutes max. Is is located on the Throttle housing and is related to the Throttle (the gate) opening/closing.
0. Wait until the engine is completely cooled!
1. Disconnect the Negative side of the Battery.
2. Disconnect and remove the Air Cleaner to Throttle house.
3. Remove the Throttle cables (pull cables forward and rotate the cable up and over the channels and slide the cylinderical keeper out) (x 2)
4. Unlock and disconnect the connections to the throttle position sensor and the intake position sensor.
5. Remove the Throttle Housing from the intake. (mine had 3 x 10mm bolts.)
6. There should be a 8 or 10mm bolt(s) holding in the throttle position sensor. Remove it/them.
7. Since you have the Throttle House off, clean it completely with Carbuerator Cleaner.
8. Install the new TPS. and installation is reverse of above.
Good Luck, let me know if it helped and is there is anything else I can do for you.

It should be on the throttle body (on the top of the engine)couple screws and about 20 minutes simple fix