Let's begin with the important stuff: welcome to APUG and may we welcome you in our midths as another APUG-addicted subscriber soon.
About the shutter problem. We can't tell anything definite based on what little information you gave us, as there are different types of TP shutters. Perhaps you can post images to clarify the situation and we can talk you through the spring problem.
However, if you've never done this before, you might want to consider sending the shutter away to someone who will fix it for you. Perhaps Bert Saunders, who can be found on Graflex.org, can be of help. He has repaired many curtain shutters before that may be similar to yours.
In theory, we could probably fix your shutter as well, but we are not into commercial repair or anything. Besides, we are way too busy to take on anyone else's repair jobs. We'd be glad to find the time to finish our own TP shutter projects.
For replacing the curtain: I can recommend the shutter curtain material sold by MicroTools - you can place a custom order for the size you need. (Up to a maximum width of course).
Don't despair though, these shutter curtains are rarely really way beyond repair, unless you've got woodworm or something. Be sure to check out the cog wheels are still okay and have all their 'teeth' - replacing one of these can only be done by machining a new one or stealing a good one from another shutter.
Hope this helped a bit.