set e brake
That can be the throttle position sensor, MAP sensor, oxygen sensor or any of a number of other things. If the check engine light comes on it usually means that the computer has stored a diagnostic code. Borrow, rent or buy a code reader for Early GM and see what codes you get. The computer is trying to tell you what's wrong, just let it help you fix the problem.
You're also going to have to drop the crossmember if you're changing the gasket
As with all cars, the oil collects it the lowest part of the engine. That's why your oil drain plug is where it is. You can see the oil pan by jacking up the front of the car and putting it on proper jack stands. NEVER support a car on just the jack; I speak from painful experience. If you wiggle under the engine and find the lowest part where the drain plug is you will be able to see the oil pan bolts going up into the engine block. In fact, the oil pan itself with trace the size of the block, so you will probably see a dozen bolts or more around the edge of the oil pan. If you want to remove it, make sure you drain the oil first, and never drain the oil when it's hot or you will be severely burned. If you remove the oil pan, you will need a new gasket when you replace it.
if back brakes are drum i would think they are worn out not allowing pistons in wheel cylanders to return. also could be valve in master cylander.altho that would cause all brakes to lock up. if disk brakes your calipers need overhauling or replacing
It should be located at throttle body. It will have a connector going to it. It reads the position of the throttle plate. There is also probably a idle controller located near this also. This controls the air around the throttle plate while it is idling. I hope this helps you.