91 Eclipse Fuel pump help

I have a 91 eclipse, everthing tests out good. and we never hear the fuel pump running. And it was tested to make sure its getting juice. I bought a new fuel pump, and i notice there are two large, circles in the back of the fuel cell. I notice the one on the right is smaller. First off which one is the fuel pump, and second the screw are rusted really bad. I have been spraying them with pb blaster to help break them loose but no luck. any ideas or suggestions is greatly appreciated.

Thanks Chase