Mmmmmm checker plate....!
If you buy a landy you can buy all the panels ready to fit!
You are prolly needing 2mm plate for sills and non load bearing surfaces. My Wing tops and load bed are 3mm and survived well.
It was cut using a plasma cutter, plate has a tendency to fur up quite a bit.
Bent using a larger bendy press thing. Failing that (if you don't have access to one) clamp a bit of wood either side of where you want the bend and beat the **** out of it with another piece of wood and a hammer. Can get all sorts of funky shapes made using that.
Fixed using double sided sticky tape, or my prefered technique is lots of rivots. (Rivot guns are well cheap if you don't have one). I decked out the back of the 90 for £130 as a guide.