A CLA would probably reduce the shutter sounds by a bit. It would also probably make the entire camera smoother to operate. It they've never been serviced, there is almost certainly at least some dried/gummed up lubricants that should be removed and replaced.
I think I read somplace that the fabric shutter replacement was about $400... and that was some time ago. Not a viable option, unless the camera actually has a bad shutter that can't be fixed.
If you want the sound of an M3, I'd suggest you try one. You should be able to find a good user for the cost of the fabric shutter.....
They are nice cameras, no question, but not that much of an improvement over the P. In fact, with the multiple VF built-in, some people would call it a step down.... all a matter of choice.
Harry