The front lens group simply unscrews from the lens mount- at least on my GW690, first model (no lens hood). Just to the front of the shutter ring is a thin- 2mm? black ring. If you can get a grip on this, the whole front group unscrews- many many threads, maybe 6mm of distance? Go slow, over soft surface, etc. in case it drops. Try a rubber pad to grip the outer edge of the lens?
Inside are three small screws around the outer edge of a flat flange, going into a brass plate. These screws hold the shutter dial in place, best as I can tell. Well, I am not going to unscrew them just for fun, but the shutter dial is the same piece as what these screws hold. I bet your screws have come loose. A little tightening might solve the dial issue.