As for the plastic slides, they will wear eventually and rattle a bit but will give serviceable wear for a very long time. I`ve never had to replace one and I`ve done more miles on Bigs than anyone.
The fuel lines are a mixture of 6mm and 8mm, but there`s a catch

After trying to use aftermarket fuel lines and nearly burning my goolies off I will now only buy genuine Suzuki fuel lines. Not cheap, but they will give you many years of problem free service.
As Ladder says, you will probably need to replace O rings and there are quite a few but the ones around the needle valve housing invariable crack and leak fuel into the engine, so definitely do those.
Part no 13374-35C00.
I would personally only use OE ones, though Tourmax are made in Japan and should be OK. Don`t trust any of the Chinese copies.
Phone Michelle at Robinsons 01227454366 and mention my name for 10 % discount.