I am surprised Zip Dee didn't send you instructions. I have heard they have good customer service. Maybe a call placed to them and you can get detailed instructions for the fabric replacement.
We got a 1979 Sovereign
last summer and one of the first things we did was remove the street side Zip Dee awning which is 20' long and comes out about 4'. When we got ours, the awning material was put on upside down and the strap was also ripped in the middle. The whole thing came off fairly easy but read the Zip Dee website on removal. The arms are wound tight and will hurt you or the trailer if taken off wrong.
We re-stitched much of this awning while it was off since the stitching was coming out. We also replaced the cord at the top (which had dry-rotted) so it would stay in the aluminum slat tracks.
The hard part for us wasn't the riveting or removing of rivets to the tube, it was getting the material on and off the tube. It is a long awning and trying to slide the material over the tube the full length is like trying to put on a pair of tight jeans with legs 20' long. New material may be easier to slide on depending on how tight it is.
Once you have the material on the correct way, drilling new holes for the rivets and attaching the awning are simple. Make sure the awning material is on the right way (flap at the open end should fall downward once opened). Also our strap got riveted to the tube after the material was put on and between flap and awning so the flap hangs down.