monsoon Stereo Install on 2002 Sunfire

I hope I did not make a mistake, but I purchaed a Monsoon AM/FM/CD to replace the unit in my 2002 Sunfire. It looks the same as mine although the performance in my other Pontiac with a Monsoon unit was great. Is it possible to put it in my Sunfire and what do I need to know as far as any other things like keyless entry, or other data that may be no longer available if I change out. I also have a Delco Monsoon amp coming to install. Do I need any harnesses and where does the amp go? Am I missing anything? I guess I am getting senile, because I thought it would be simple to change out? Am I better off not changing the unit?