Fuel tank leak

Hi, this is the first time I have posted on the forum. I have a 1996 super custom 4x4 and am based in Scotland. I noticed a fuel leak from the fuel tank area and took it to my garage who said I needed to replace the tank as it was corroded at the seams. The garage says I need to source a second-hand tank which they can fit. The fuel tank has an indent for the spare wheel. I have tried to find one on some second-hand breakers sites but cant find the correct category to describe my vehicle so am rather stymied from the start. My questions are 1. how do I find the specification for the fuel tank; 2. failing finding a tank is it difficult to remove a fix a fuel tank myself. The garage says I will have to scrap the vehicle if I cannot find another tank. I am planning to "do-up" the van gradually (retirement project) - I am no mechanic but plan to learn on the job! I would be very grateful for any help -