Hi Gypsy, not sure about vans but did my Ute a couple of months ago. 2 Bows and a thin wire which clips across the cabin in front of where the interior light goes.
1. Much easier with windscreen out, more room, easier to stretch etc.
2. Have some sections of pinch weld cut into about 10cm pieces to clamp over and hold the liner in place. Found this info on the web AFTER we had done the Ute, would have made the job much easier.
3. We fitted it to the front, then sides and rear last
4. Make sure you mark all the holes as you go, mirror, sun visor, light and coat hooks etc. I am going to have fun trying to find the holes for my Seat belt holder hooks.
5. Use good quality contact adhesive, you don't want it to go wrong.

GOOD LUCK - not a hard job but very hard to get it looking 100%

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http://cgautoupholstery.com -check out this website, has some photo's and tips for headliners