Im going to install an amplifier with one 12" sub. Can I use the car stereo instead of buying a new Indash? if so what do i need and where can I get it? Thanks!

You'll need a line-out convertor. I wanna say they're about $10-$15.

Where can I purchase one? any website? I'm kind of new to this stuff lol.

eBay?

the retail for around $35 and can be had from best buy, circuit city or any 12v installer.

http://shop.ebay.com/items/?_nkw=line+out+converter&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=scion+line+out+converter&_osacat=0

they should, you just need to tap the proper wires, which a quick trip to google will help you find

Think Best Buy still carries them as well as Crutchfield and Sonicelectronix

indeed

This is what you're looking for...

http://www.crutchfield.com/p_142SLC4/Scosche-SLC4.html?search=line+out+converter

^that is for a 4-ch amp and he needs a 2-ch but i hope he gets the idea of what he is looking for.