Where is the egr valve located on the 7th gen Monte Carlo? Where can I buy a cheap replacement one?

 

EGR Valve can normally be located atop or next to your engine intake manifold

This link will help give you a lot of information on how to change the egr valve, diagnosing if the problem is the egr valve

Part 1 -GM EGR Valve Test (P0401, P0403, P0404, P0405).

There are links within the link I posted that will help you.

 

That's an extremely helpful link, thank you very much!
My car does not have a check engine on but still has all the other issues, is this possible?