question about installing aftermarket cd player

ok so i've heard all this stuff about if your civic came with factory installed keyless entry..it is in the radio and must buy reverse harness and keep it hidden behind dash to install new radio. so just to get things straight...i bought this civic about a month ago and it has an aftermarket casette/am/fm radio in it but it is a very old piece of junk. it is serious crap. i have not taken a look from behind the radio in the dash but the civic had keyless entry/alarm installed separately (brand name clifford), so i am assuming that the previous owner has already gotten rid of the stock radio and it will be as simple as trading them out for me when i get my new cd player. Also i have another question...do wiring harnesses for civics fit all cd players? or do i need a special wiring harness for a civic and the cd player im gonna get? if this guy has already installed an aftermarket radio (although very old)..does this mean he already has a wire harness that i can use with my new panasonic?

if you have a 98 honda civic with a aftermarket alarm on it all ready than you don't have to worry about the factory keyless entry system.

Only for 97-98 civics