Hi Leif ,
It is not very difficulty to replace the headliner if you ever did it before.
If not like in your case this will be a real nightmare.
You will need help and after all it will not be looking good.
My first one in a Beatle was so bad that I had to bring the car
to a upholstery shop.
Luckly I couldt stand around when they replace the headliner
and catch the hints and tricks.

I recommend that you get professional assistens when you do the headliner.

Did you get the Bid for your conversion ?

Sincerely Detlev
Vanagon Projekt
925 606 8797