cambelt 2002 LT28 95 TDI?

I own a VW LT28, purchased of a friend! new years eve the van came to a halt, The engine didnt jam or lock up. after inspection I found the water pump bearing failled, causing the belt to slip a tooth or few.
I live very remote in mid wales where mobile mecanic's are has rare as hens teeth. I am cabable of changing most parts, even full engines & gear boxes, although I have never changed a cambelt. I now have a new belt kit & a peter russek manual. I have removed the front of the van. So far am unable to release the large nut on the crank pulley, that was why I ordered a manual, living where I live meant due to the freezing condition I only recevied it yesterday. it is a help but now I'm unsure if its possible to undo the crank pulley with a airgun? if so which way? can I do this without the special tools required? is it possible to knock somthing up in the workshop? or use other clamps or grips? can you please give me some guidance. I wish getting someone else was a option. until I get back working I cant afford to pay a garage bill.