It matters if you will be pulling more voltage. If you plan on converting to 12 volt and or if you plan on additional power required extras.
As far as expensive you would need to decide if you wanted to buy a fuse box at a FLAPS and design your own set-up or buy a ready made.
Below are a few links to look at for information. Also Painless Wiring is a simple system and can be found locally at most Auto Zones.
http://www.americanautowire.com/American_Autowire__800-482-WIRE.htmlhttp://www.painlessperformance.com/
