HELP- 1984 GMC 3500- fuel leak from tank

[2badgn]

I had a new fuel sending unit installed months ago by my local Chevy delaer. When I noticed after the unit was installed that the gauge was better but not 100% accurate, I brought the truck back to my dealer. Dont know what they did but now I have fuel leaking from the tank. THe truck was at the dealer for 2 weeks and the tank was full when I brought it there. It was near empty when I picked it up today. They fixed my horn by replacing the turn signal switch but now I have a fuel leak-- ARRRRRRR!!!!

I tried tightening the bolt on the side - but it kinda made it leak worse. By loosening the bolt a little, I got the leak down to a drop- Have a bucket under my truck now.

Didnt try tightening the other bolt bc I didnt know that it was also leaking but much less than the bolt on the side. Going to bring it back to the dealer. But in the meantime, do u think that its a washer or do I need a new fuel tank? Help please- Want to fix this ASAP.

Thanks
Frank