I usualy fill my tank once it hits half full so its around the full point a fair bit, I noticed yesterday under where I parked a spill of some sort, looking up at my fuel tank I could see a wet patch coming down from near the top of the tank.

I took the seat off and removed the panel and I noticed a damp patch around the fitting where the pipe goes into the tank. So I think its just with it being full (right up the fill pipe) that its got a little pressure on it and its leaking slightly. So whats the best fix here?

Secondly the fuel guage has been doing stupid things lately, the tank is near full give or take a gallon, and the guage is going up and down even when in a stopped position on the flat. Don't think the two things are connected apart from the fact there both on the top of the tank. There is no spill or damp around the guage sender, so I don't think it could be a problem with diesel. The sender is only a few years old, so could it be anything else, other than a dodgey unit?