Prices tend to vary with suppliers, there does not seem to be a standard price. When I need parts for my Chevy Celebrity I survey the local sources and buy the best deal I find.
No Chevy Celebrity ever had a 4.0L engine
The spark plug gap for your 1989 Chevy Celebrity 2.8 V6 is .045".
Which engine does your car have?
On a 1989 Chevy Celebrity the timing is controlled by the engine control module, there is no specification or provision for adjusting the timing manually.
Yes with modifications.
The petcock on a 1989 Chevy Celebrity is at the bottom of the radiator on the drivers side.
On a 2.8l v6 it is at the front of the engine behind the ignition coils.
According to one source I found the weight of a 1989 Chevy Celebrity varied between 2751 to 2928 pounds. Actual weight of a given car would depend on engine, transmission and other options.
On some cars there is a sticker in the engine compartment with a belt diagram.
The oxygen sensor on a 1989 Chevy Celebrity is located in the rear exhaust manifold on top about the center.
How to change the power steering pump depends on which engine your car has.
I found a site that listed the curb weight of a 1989 Chevy Celebrity at 3100 pounds. Of course that would vary depending on the engine and other options on a given car.