Thank you all for all of your help thus far.. So after talking to alot of people, I have decided that the best method (affordable, easy, etc.) for me to fix my gas tank which is rusty only on the inside and holds fuel fine, is for me to use the POR-15 automotive fuel tank treatment. The price is somewhere around $54 and I can do it myself. Is there any thing I should be aware of before doing this? Or is there something I should do before using this (besides removing the fuel from the tank), like shaking around nuts and bolts inside it? What is the best thing to do? Thank you all very much!