Hi All, I have an '03 Civic EX Sedan with power door locks and want to add a keyless entry system. I just purchased the car and it has an aftermarket stereo system installed, don't know if that makes a difference. Can a keyless entry system be installed? If so, is this something I can do myself (fairly easy) or would I need to have it installed? What are the best brands of keyless entry systems to look for and how much would it cost (roughly)? Thanks