1996 Chevy Lumina How to Replace Water Pump

Drain cooling system
Remove serpentine belt
Unbolt the water pump pulley; the water pump is behind
Unbolt water pump from engine
Scrape old gasket off engine
Install new pump and gasket in reverse order (make sure you use a torque wrench)
Refill with fresh coolant
With radiator cap off and bleed screws loose, turn car on and let it idle
When coolant starts pouring out of radiator put cap back on, when it flows out of screws tighten them.
When car reaches normal operating temp turn it off and let it cool down (completely).
Re-check your coolant level and add as necessary.
You're pretty much done.

Hello there,

Glad I could help.
The only way to know what's going on with the check engine light is to check the code(s): if you have a code reader/scanner plug it to your car and retrieve the code(s). If you don't have such tool, take your car to an autopart store (O'reilly, Autozone, etc) and have them retrieve the code(s) for you. Usually they do it for free. Once you have the code(s), you can report back here with the code(s) and I'll try to help.