Thanks for the advice! I got it all out, power-washed, vacuumed, and enzyme-treated. It looks like I am missing a couple of the body plugs (no rust though!)... Where can I get replacements for those/can I fabricate something that would work?

I broke a gallon of milk in the backseat floorboard a couple weeks and no amount of shampoo and cleaner can get the smell out. GM no longer produces the whole carpet, so I'm trying here... Smoke-free and pet-free is preferable. Thanks for any help you all can provide.