A 4-channel amp isn't the best choice for powering subwoofer(s). A monoblock is best, followed by a 2-channel. If you understand the basics, have a little mechanical (and electrical) aptitude, you can usually do the installation. But it will help to have someone who is knowledgeable and has done it before to assist you.
For a stock receiver, you need a line output converter similar to this one:
http://www.davidnavone.com/cart.asp?14&pid=362
A cheap Scosche from WalMart will work, but the sound quality will suffer.
You'll also need an 8 gauge wiring kit:
http://www.darvex.com/store/pc/viewPrd.asp?idproduct=82&idcategory=2
Here's a generic install video. For more specific information about how to run the power wire through the firewall, route and conceal wiring, etc, you may want to browse some of the posts on a Honda forum.
http://www.youtube.com/watch?v=VAQoYTmHZd8
There's also some good information here:
http://www.bcae1.com/
And on some of the online retailer's sites. Crutchfield is a particularly good place for install information.
http://www.crutchfield.com/S-yMAVB8k94J2/