quick questions straight to the point.

does the factory radio have a spot to add a subwoofer? if not what can i do to add a sub with out replaceing the deck?

no it does not have component outputs but there is a company that makes a plug you install between your deck and the factory harness that does have the outputs. i cant remember the company, but do a search for "amp" and you should find it as its been mentioned many times here.

Ive done a lot of excellent sounding stereo installs in trucks. If youre adding a sub the only way to go is to get rid of the factory deck. I understand the stock look issue but you cant make a sub sound as good as it could with a factory deck. just my .02 though

You can install a Line Out Converter that will have the jacks for the Rca's (This is what I did) or get an amp with high level inputs. High level inputs usually get the signal from your rear speaker wires. The line out converter converts the signal from the speaker wires to the RCA type jacks. It is true that if you want the best sub controll and sound to go with an aftermarket Head Unit. I didnt want to mess with the factory Onstar and my steering wheel buttons so I opted to keep the stock unit. :D
Rick