I saw this Disco for sale on facebook this evening and what he is asking is ok in my opinion if your prepared to do the work yourself, at least he is throwing in a sheet of steel and the box section etc for the sills to help you out but you will still need a new boot floor panel etc.
But as said above expect to find a lot more rot than what you can see and its going to be a lot of hard work and forget the arc welder, I have been there and done that years ago and its bloody hard work chasing holes, so if you go for it buy yourself a decent little mig and you will be far better off.