Taking gauges apart to restore them is in same category as taking anything else apart on a restored bike. Its a good thing (as long as you don't mess it up). The early gauges are very ez to take apart. If you roll back the odometer to "0", just tell new owner you did so. If you leave odometer alone, thats ok, too. When apart, you can clean inside of lense and polish the clear plastic. If you have a couple sets of gauges, you can mix and match the best parts. The repop faces require a tricky decal installation and look a little phony.
Nice gauges are what you want on a nice bike.