Don't lose the little plastic washers off the lugs, and likewise the little shim or shims atop the shutter plunger!
ruby.monkey, Tomosys probably made a better job than me but I have a set of notes I was emailed that got me through a rebuild of a Prestor shutter - PM me if you are interested, and I'll find them.
Take lots of pics on the way in and out again - they are about half as complex again as most other shutters.
In my (very limted) experience, the big problem is that eventually one or both of the two springs that drive the actuating ring stretches. Once this has happened, you need a spare shutter, as I cannot find a source of springs man enough for the job.
On the other hand, if you have a completely locked shutter, there is a neat "gotcha" if you wind on whilst pressing the shutter down... This locks it solid, but unlocks if you take the top off and prod it - strange flaw, but easy to fix!
Hope that helps,
Adrian