Like i said i have an 02 monte and i have a check engine light that just came on so i looked at the engine and noticed the coolant resevoir has a sort of thick black fluid in there and it kind of looks like oil im not too sure.. I havent delt with cars too much but i know thats not right at all and had some other people check it out too. If anyone has any clue of what it could be it would be very much appreciated. Im in the marine corps and need to get to work everyday so i cant afford to have a problem like this one.

Welcome to AF!
Sounds like you have a sludge problem. I'd get the cooling system flushed out very well, ( which will be hard to do if the gunk is severe.) I'd also check to see if your lower intake manifold gaskets are leaking. Air can infiltrate your cooling system and cause the coolant to sludge up.

Alright thanks a lot, i will do just that.

Semper Fi