Re: Replacement gas tank
Generally, you don't want to buy an old used gas tank unless it's aluminum and in good shape or is relatively clean plastic.
Depending on how old your boat is you probably won't find a salvage tank anywhere but craigslist or ebay. If it was built in the last 5-7 years then maybe.
The best way to get a cheap replacement tank is to measure the space you have for it and find a moeller or other aftermarket tank the same size and install it yourself. Alternatively check greatlakesskipper.com for an OEM tank that will work (surplus place).
Replacing a tank is easy if the old one is out, don't stress about fittings, the plastic tanks pretty much need to be tied down on a solid surface and that's it.
Erik