oil light problem

Okay, I 've got a '91 GT 5spd with the 2.2l motor. Recently my oil light has been staying on longer then normal after it starts. But it doesn't do this everytime, and when it does it goes away. Then what really got my attention was today after I changed the oil I went to start it and the oil light actually stayed on. I turned it off then turned it back on to see if the light would go away, but I didn't. So then I reved it up and there was some loud knocking then the oil light turned off and the engine returned to idle and I never got the knocking noise again. What could this be? Do you think my oil pump is going bad?

I would purchase a pressure test gage and check your pressure. From your description I think your strainer might be plugging up. I would decide to pull the oil pan based on what the pressure gage says.

Okay sounds logical. But I've never done that before so if I get the oil pressure gage where will it hook up to and what should the pressure read?

Unscrew the oil pressure sending unit and screw it into this hole. Usually the gages are on a hose so you can hold the gage and have somebody in the car start the engine and do what you ask. You should have around 20psi at idle and around 60psi at higher rpm's.
Depending on the brand of filter you have a good filter should have a check valve. Use at least 10W30 oil
A worn pump has a hard time getting a suction with 5W30