Fastest, easiest, and safest way is to just drill a new hole and put a rubber gromet in it....saves a hell of alot of time. installing an amp is the easiest thing in the world to do, but if you screw something up you could damage not only the amp, but the car's electrical system as well. If you have any doubts in your ability to safely install any equipment...seek a professional out and watch how they do it....once you see it then you shouldn't have problem afterwards. It would be very unwise to attach the main power for the amp to the positve post in the fuse block...very unwise.
As far as wiring here is an end all chart:
Attachment 5880