cutting it up depends on what you want your finished vehicle to actually look like/be used for?
There are dozens of bobs out there on the net to look at for inspiration, I have not done a Disco but did a RRC a number of years ago, pretty much spent a weekend getting all the bits together I thought I'd need and the following weekend it was chop chop, perfectly doable in a weekend.
One piece of advice for this is remember you'll need to empty the fuel tank, relocate it or get a purpose made take made up.
A sheet steel edge joggler for the roof helps to get a little bit of wiggle room when re-fitting the rear section of the roof, ok it's only 10/12mm on either side but as long as you are precise with your cutting it's all you'll need, it helps seam welding the roof panels & gives a small void for the filler to make it look nice.
I went through about half a dozen 9 inch cutting discs, on the 4 1/2 inch grinder it was couple of 1mm slitting discs, few 3mm cutting/grinding discs, a couple of different grade flap wheels and a grinding disc.
I got a load of off cut 2mm plate from the scrap yard for the internal and external plating of the chassis rails and some 1.2mm sheet steel for the body work, a mate who worked for CAB glass cut me the laminated glass for the new shaped rear windows.
I can not stress enough the need for datums and precision in your cutting and fabricating, I made a few mistakes with it as it was my first, all of them are avoidable if you think logically about what you're doing.
Good luck, keep us posted with some pictures, we loves pictures.