Some tips for you when you've got the top cover off...
First, clean the VF/RF optics while you're in there. Zorki 5 has a really good VF so make sure you're getting the best from it.
The winder gears are relatively complex. It's been several years since I did mine but from memory there are three screws holding a plate in position, with the gear-mesh being adjustable via at least one of those screws. If you search the net, I'm sure there was a page explaining how. Make sure you adjust them so that the mesh is close enough for them not to slip but loose enough to be free. The winder on mine is absolutely the best of any of my FSUs, so aim for a smooth action. Zorki 5s are noted for grinding winders and it's only because someone mis-adjusted the mesh.
You'll also find re-fitting the winder spring is a bit tedious, patience will reward you here. Lastly, when you refit that left-hand threaded collar, make sure the threads are clean and lightly greased. Tighten the collar with your fingers until you feel the thread stop. Leave it at that, don't be tempted to tighten it with any tool! Periodically, loosen it and re-tighten finger-tight. They self-tighten in use and doing that will ensure it will come off again in future, if needed.
EDIT: I think the nickname comes only from the fact that it looks a bit like an M3 and is a similar size.