Re: gas tank
Take it out of the truck and throw some degreaser in it and wash it out good. Its ok to use a water based degreaser and a water hose. A pressure washer would work better, but not required. Just be sure and dry it out good. The hardest part about it will be getting the tank out. If nothing else take it to a car wash.
I love it when people do things right
Unfortunetly I dont always do that lol