Do I assume correctly that your camera is one of the earlier models, with a fixed back, rather than the removable backs usable on the Super or Pro models?
If so, I'll agree that your camera is heavy!
Mamiya made left hand grips for your camera with a built in mechanical trigger release. I find the left hand grips really helpful on my Pro model (and the Super models I had before).
I also really like the focus assist handle that Mamiya made - it will fit on your 80 f/2.8 lens.
And that strange feeling with the film advance - I think it is because the wind function advances the film and cocks the shutter at different parts of the wind.
Have fun - the lenses are great, and the cameras are eminently functional.