Rolf - Don't let this project scare you - it's super easy.
Some 30lb dacron backing (25' or so), a griffin bobbin threader, and you're in business. Just look at the net and how the cord is run before you cut the old bag off, and it becomes pretty obvious as to how it is attached. Start at the handle side of the hoop.
Took me less than 20 minutes to do. If you don't like the looks, just start over. I dyed my backing black with RIT dye, and the resulting finished product looks better than new.
The measure nets are easier, but they don't look as good on a nice frame, IMHO. The Ghost net bag is next for me - I'm gonna dye the backing to match the frame. :-D