Ok, so I'm chilling at the beach and did some research for you.
The RCA's you see are output only, used to send a audio signal to an aftermarket amp, if you want to. Let's say you wanted to install a Subwoofer for some big boom, one of the two RCA outputs would light the way to boom.
On your unit, there is a port called a "IP-BUS", and can be used for a couple things, most commonly to add an external CD changer; BUT WAIT, THERES MORE! Lol
There are cables available that will allow you to connect an Aux input to the IP-BUS. As an example, look up "CD-RB20". There are versions of the cable that will go from IP-BUS right to a 3.5mm headphone jack. Thus giving you your Aux input!
As for the antennae question, I honestly don't have a clue if you'd need an adapter. All the units I've installed over the years, the antennae cable is an exact match. I'm about to leave to beach //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif so I can't look up your car for you, but I'm going to guess you won't need an adaptor.
I don't know how links work in the forum, but Here is a link to your unit's manual:
https://www.pioneerelectronics.com/pio/pe/vgn/images/portal/cit_11221/49731CRD3301A_200012301325447930.pdf
And this is a link to your unit's installation manual:
http://www.pioneerelectronics.com/pio/pe/vgn/images/portal/cit_11221/49734CRD3311A_200012301332357300.pdf
I hope I helped you out a little bit. Your year Chevy should be a pretty easy install, but if it's something you haven't done before I would highly recommend you have someone help you, or watch some vids and browse this forum for advice. Number one rule is always disconnect the battery before installing any audio equipment. Have fun!
