take a look here http://www.sheriart.net/honda/
There are well written instructions with pictures on the first link.
Not to steer anyone away from this forum but...there is plenty of info there (second link).
Don't expect the kid working at Radio Shack to have any idea what you want or need. I spoke with the "manager" and she was clueless! It was funny but sad at the same time.
I used a hot glue gun to secure the relay to the motherboard on the radio. I also got a small project box and mounted it inside of my left faring pocket for the jack and toggle switch instead of drilling a hole in the top of the radio for this.
I did the entire mod in an afternoon taking my time. You have to solder with a pencil tip iron. I also recommend completely removing the capacitors instead of trying to pull the leg through the board. I also used a solder sucker (don't know the correct name) to unsolder the caps. Solder wick will work too. I used silver bearing solder. No acid core! This is not a radiator it's a fine piece of electronic equipment and you should treat it like one
If you get stuck, ask questions as I'm sure there are plenty of folks here who have done the same thing.
Where are you? Perhaps someone (like me) is close enough to give you a hand when you tackle this mod.
I'm in Virginia