Bongo Fury

I have a Bongo Aero... I don't recall the year but the point is the sills are quite rusty and there's no welders on the island I live on who are capable of the repair. I have learnt how to weld and can do practice welds but I'm trying to work out if this is even worth fixing or if it's too far gone. that and tips in how to weld it or if there's anything that may be broken (due to typical stuff that wears or fails on this vehicle) that would be good to know
here are some pictures.
Apologies if the way I've worded anything is odd just not use to writing forum posts

Very difficult to tell from the photo's !! It looks quite extensive not sure if its running into critical load supporting areas as well which you don't want to touch perhaps as a beginner.