Well, I usually stumble my way to some sort of success with repairs! lol
I haven't had to do much on either of my 16mm machines, one of which I've had for 25 years! (knock on wood.) On my Elmo 16-CL, when I bought it, I immediately order Urbanski's new rollers. That was pretty easy to install, but I did need to email him since I didn't note which rollers go where before I removed the old ones!
I have the service manual for that machine, and though these things are usually useless to me, it actually helped me fix the auto-loop-resetter, which wasn't doing anything. But my fix was my own improvisation. I needed to roughen-up some kind of roller so it would have enough friction to engage the loopsetter. It uses a Rube-Goldberg system, and I'm not sure why you can't manually reset the loop as on their Super 8 machines. I had tried to come up with a solution to somehow build a manual switch for it, but it never got past it being just a thought. The way it works now really looks like something out of the "Mousetrap" board game!
I would have given up the hobby years ago if I had to rely on sending my machines out to be repaired. Shipping alone is expensive -- I've never known of a local place. Back in the VCR days, I brought the same machine back to a repair place 2x, and it was never fixed properly. Didn't cost me anything since it was still under warranty, but it still chewed up some of my VHS tapes, and that wasn't even the original problem!
And as I've mentioned before, almost 30 years ago I bought my first Elmo, the ST-1200HD, that was supposed to be fully serviced, but after a few weeks started to run slow, and the next thing you know I'm ordering belts from Elmo in Canada. They had to send me belts several times because the first ones didn't fit!
There was a place that used to advertise in "Coming Attractions" from Steve Osbourne that was actually fairly local to me back then, yet I remember someone writing an article in that same publication on how they used that service to "fix" his Elmo, and when he received it back, it no longer fit a 1200 foot reel!
I know you had a guy on your side of the pond, Tom, who has fixed your machines before, but I think you said he no longer does it. At least you were lucky that he was reliable when he did work on your machines.
I consider the repair part of the hobby, and sometimes part of the fun. But I will never claim to be an expert.
I've been buying a few machines recently that needed work, but I knew that going in, and luckily most of the parts are available from Van Eck. Now I'm just waiting for them to arrive, and with some luck I will have a few more "almost as good as new" machines for a fraction of the price had they been "mint" and "serviced"! Again, knock on wood!