First the lens you are taking the shutter out of has the same flash sync as the one you are putting into? That's generally the difference between shutters on the RB lenses.

RB lenses are opened form the top down. Most need to have the name ring taken out first. The front n rear cells unscrew like light bulbs. Once the cells are out take off the front cone. You'll see a few screws, take em out and take that layer out. Then take the screws out of the next layer and you'll be at the shutter mount.

Then turn the lens over and take out the retaining ring that is around the where the rear cell was. That will drop the entire shutter in it's mount in your hands. To get the mount off, there are 3 screws in the side of the mount that keep it in place. Take off the thin tin part, then loosen the 2 screws, one at each end of the preview slide. The third is the X/M slide spring, a stainless steel flat V shaped piece. The shutter is now free and you cna do what you want with it.

Work in good light. Keep everything organized, screws are put into a pill organizer in the order of operations. Work on a mat so nothing bounces around or mars your lens.

Most of all is have fun n relax. If you feel you are getting in trouble, leave it alone and come back tomorrow when you are feeling fresh again.

Take a look at my pics of lenses on Joe's site. There is an exploded view of one of their early shutters. There are about 5 or 6 variations of shutters so don't think yours is damged because it's missing parts or doesn't jive with the diagram.