1995 GMC Jimmy Sensor locations- Knock Sensor, TPS Sensor

My 95 Jimmy check engine light is on. The code readout says TPS sensor faulty, and Knock sensor faulty. I looked up on-line and see what they look like, but exactly where do I look for them? 4.3 Liter V6. FInal question- when I replace the sensors, does the light reset? Or is there a trick to resetting the light/clearing codes?

This is a 95, so it only has the older GM check engine light and the "key" type plug under the dash- not an OBD. Code is 21 and code 43.

Also- side note: I smell gas fumes- the mechanic says the fuel tank is rusty and leaking, but wants a thousand bucks to replace it and the fuel line. This is a snowplow truck only for the driveway. Gas milage is horrible, about 5- 8 MPG. Any ideas? Is it the leak? It runs as if it is running very rich.

thanks in advance.