There is a tank repair kit that will work to "weld" the tank and fitting back together. All the reviews of the kit are positive and the company says that the repair is stronger than the original tank. You might want to do some cost comparison between a new tank and a repair kit and a couple hours of your time......
Here's one link to the kit:
http://www.pplmotorhomes.com/parts/c...ank-repair.htm