I had a leak in the left hand side tank due to a weld fracture.
I elected to have the tank replaced rather than repaired and this was done by the dealer. In either case the tank needed to be removed from the car and split apart from the plywood base.
I'm not sure if it came out through the top or bottom and I think they took the back wheel out but don't believe they had to strip the back end down any further.
It's an aluminium tank so anyone who can weld ally could repair it.