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I have to disagree on getting a professional to install your CD player, if you are able to get your old unit out with no problem then you should be ok from that point. The worst you could do is dead short your live wires to ground which will result in a blown fuse and not a ruined car, and that is if you leave your battery hooked up while doing this which is not a good idea. The best bet is to go to Canadian tire, Wal-Mart, or any place that sells car stereo accessories and find a harness that matches your car year and model, also in most cases i've found you'll need a bracket that will match up with the old screw holes that held your original head unit and fits a standard cd player size, Honda's almost always need them, these brackets will most likely be right beside the harnesses at whatever store you go to. The bracket is usually quite easy to install.
As for the harness, the one you buy is to plug into your factory harness or harnesses ( some cars require two, one for power and one for speakers) and the other end will be bare wires which should match the colors of the wires from the harness that came with the cd player.....solder these together with colors matching and you should be good to go.
after doing this a few times you'll find it isnt very difficult but some vehicles are equipped with their own factory amplifiers which can lead to having to bypass the amp or use the low signal outs on the deck so you don't exceed the maximum input power on the factory amp. so if your car is a higher grade model you might want to think twice about doing it yourself but if not this should be a good learning experience.