Comment by boesboes

That really depends on the sizes, if the face and movement are the same size I expect it should be easy enough. You will need some tools and fine motor skill, but no where near as much as you need when taking apart a movement.

Looking at the two watches you mention, the navigator has a Quartz Harley Ronda 373 movement and the diver has a ETA 2824-2 movement. The 373 I can't find the specs for, but from an ebay auction it seems to be a 11½’’’ diameter. The 2824-2 is the same diameter. However, all 11½’’’ ronda quartz movements I can find are 3mm thick where the 2824 is 4.6mm. So what I'd expect is that it will fit, but you might not be able to secure it properly. It really depends on how the movement is held in place. Perhaps you can fabricate/3d-print a spacer for that.

Another consideration is the lug stem, that might not be the right size. To long is solveable, to short means buying a replacement. I am also not sure wether the stems can have a different thickness, to thin and it wont be waterproof, to thick just won't fit.

You could probably try without destroying anything (no guarantees ;)), you are not really touching any of the fragile & tiny parts. But you will atleast need tool(s) to open the cases, they might be different, and a tiny screwdriver to release the lug. And I wouldn't count on it remaining waterproof, not sure.