Really easy to do.
As for material you can use almost anything.
I used a double bed duvet cover.
Start by removing the sun visors and then remove all the roof grab handles.
Next remove all the a,b and c pillar covers.remove the light switches and anything else holding the lining up.
The roof lining will have to be removed via the boot.
Once removed,place the material over the top of the lining and cut out the shape you require.
I removed any sagging old roof lining and sprayed the roof lining with material glue.
Place the new material on top.
This probably isn't the best guide but will give you a little idea.
Remember to post once done