If its the amped system, the Metra 70-5513 plug should be a plug and play amp bypass and take no more than 10 seconds to install once you get to the amp, which is usually in the trunk/under the rear deck. Spend the $20 at your local circuit city to save the headache and bypass the factory shit the easy way. Other than that in the trunk, should be a typical radio install in the dash.

daltons way works too, I do it on Bose sometimes, but if it were me Id buy the plug and play bypass.