There isn't much room behind the dash for a normal in-dash radio to fit, they are about a half inch too long. Pioneer used to make a "DIN and a half" sized radio that fits the dash of Chrysler and certain GM cars perfectly and will fill the opening without a dash adapter plate. All you need is the correct harness kit for the wiring and it's all plug and play, make sure you connect the power antenna lead if your car is equipped with the infinity sound system.
The model numbers are DEH-P77DH and DEH-P47DH. May be hard to find them in a stereo store but might get lucky if one is laying around the shelf with the box a little dusty. if not, eBay does have a few of each model new in the box.
Oh and your ATC panel is on the fritz, you'll need to find a replacement soon if it goes off and never comes back on again common problem with these cars, check the salvage yards or even eBay for those too, may be pricey though!