You can also clean and coat the tank yourself. It requires some effort, but if money is an issue this method works well.
Take the sender out, and fill the tank with water. Empty the water from the tank, and refill it a couple of times to get most of the big junk out. Clean it out well, spray the sprayer in there, wiggle the tank, etc. Then cover the sender opening with something fairly rigid (a coffee can lid, etc.). Drain the tank but leave a gallon or so of water inside, drop a 6' long piece of chain in the fuel filler pipe and then roll, and turn the tank. The chain will scour a lot of junk off. It will need to be turned upside down, as most of the flakes and junk is on the top (condensation causes this). Roll it and swish it and whatever, until you're satisfied most of the crap has been scraped off. You might want to change out your gallon of water a couple of times. Tip it up and let the chain slide out, take the cover off the sender opening, then rinse it again and let it air dry.
DO NOT use a hair dryer or torch to try to dry it quicker!
You can buy a gas tank coating kit from Eastwood (I think) or JC Whitney and then just follow the directions to put a new coating in the tank.
http://www.jcwhitney.com/autoparts/Prod ... =fuel+tank Total cost about $50 and a couple of sore arms...lol...