This is a common problem, the blower amp goes out on a lot of people. If the switch works, the blower works, then all you have left to troubleshoot is the wiring itself or the amp. Which do you think it is? Search for an aftermarket amp or one on Ebay. Also, price-shop dealerships. Lots of dealerships have lower prices than your local ones if you can get a quote, most ship to you, no problem.
Owner of NPORA, mod for Nissan-Infiniti Forums, NissanForums.com, NissanHelp.com, AllNissans.com and VGPowered Forums
'88 Pathfinder: 6" of lift, 33x13.50 Swamper LTB's, Rancho 9000's, L&P Stage 3 steering system, K&N, Pacesetter headers and 2.5" exhaust, Lock-Right locker, 110A alty and electric fan swap, dual batteries, 700W+ worth of PIAAs, etc.