Done. The fuel tank didn't completely close off, but I worked quick and only got a minimal petrol shower while under the truck (it was probably a good thing that I was wearing goggles though!). Not much mess with the filter nearest the carburetor. The truck fired right up after changing the filters without issue and I let it run for several minutes, again without issue. I will keep an eye on the clear filter nearest the tank.
Thanks all for your help.
