I have had some fuel leaking from some welds on the bottom of one of my fuel tanks, so I had to pull it out and repair it.  I emptied it, removed the hoses and connections, undid six self tapping screws and lifted the tank out. 

I took some photo's to show how easy it was, after all the horror stories I have heard about lack of access on other boats. 

I took the fuel tank to a client of mine who made roll cages for rally cars.  He had all the equipment and experience for welding aluminium, and rewelded up the seams on the bottom of the tank.  14000 miles later, it is solid as a rock and shows no sign of weeping again.