The rear end of my 74 kombi has sagged a bit on one side and I am looking to try to adjust the rear torsion bars. I have a couple of workshop manuals and intend to follow them for this.
Can anybody advise if this is an easy procedure and are there any pitfalls I should watch out for?

Have a read :thumb
http://www.type2.com/library/suspens/tmadj.htm 
http://www.type2.com/library/suspens/torbar.htm 
http://www.type2.com/library/suspens/torsion.htm 

Make sure you install NEW rubber bushings on both sides both inner and outers.

Fit these with some Molly grease and you will have a smooth ride for years to come.

Dont just do one side as this will counter balance the suspension on your van.