Hey Guys, I have a 79 power wagon with 2 tanks. The gas gauge in the original tank has not worked for at least 10 years. It was that way when I bought it and I finally got around to looking at it. Turns out to just be a ground issue. Now for the issue the tank is completely empty and stinks like varnish. It was allegedly run dry by the original owner. Should I just fill her up and assume the muck will dissolve or should I yank it and clean it?

I should mention that it is a poly tank and the truck only has about 56,000 miles. Appreciate your input.
Thanks Moparts.