How do you install an aftermarket stereo on an 2004 Mitsubishi Eclipse and keep the steering wheel buttons?

Go to crutchfield.com and use the outfit my car option. everything available for your car will come up. Purchase your new deck and they can mate up a wiring harness to fit the existing connectors ( no cutting into the cars wiring ), and a mounting kit for a clean install, they also offer converters for your steering wheel controls ( if your car supports this option ) that will make your new stereo work with them. It all comes with step by step instructions.