Still looking for help with the idle?
A shaking idle isn't normally a timing belt or balance shaft belt problem, but is usually a large vacuum leak or fuel/spark issue.
I've owned a couple 944's, always done my own work and worked on a few friends 944's as well. Not an expert by any means but I have 4-5 years of experience with them
What part of Calgary are you in?
Rebuilding the starter is easy, I would have thought NAPA or partsource would have the kit to rebuild one. Personally though, I'd just take it to an experienced electrics shop, they should have all the bits on hand to rebuild it properly. Bosch likes to use commonly-sized parts in their starters. I have yet to find an electrics shop I am happy with in Calgary so I can't really recommend one. Typically it will cost ~$40-$50 for a rebuild kit, or $100-$120 for somebody to do it for you. The biggest things to worry about are either when they are put together completely wrong (i.e. don't fit or spin backwards), or the big power wire coming out of the solenoid having it's insulation break off and shorting to the body. Good thing is starters are super easy to remove (_MAYBE_ 10 minutes to get one out) so if they're done wrong it can be fixed easily.
I have a spare starter, but I forget if it is early or late. On a N/A it doesn't matter but I was going to fit it on my 951 to take its starter in to be rebuilt (it jams about 1/2 the time, and squeals like a banshee when starting)