so i went and picked out a nice Pioneer deck for my cavalier...as i was getting ready to go and they told me that because i have a 2000 Cavalier there is an extra adapter i need because GM ran a lot of the electrical parts of the car through the stock radio making it impossible to install an after market one without this adapter. is this true and are the any other suggestions/options to get around this?

you need a wire harness adapter(i believe) and an antenae adapter and you have to bypass some alarm thingy too.

it is a pain in the ass and would let a professional stereo shop do this.

Yep. you need http://metraonline.com/product.aspx?sku=70-2003T

But it's not that much of a big deal anymore.