That really depends on the person doing the work. Even though I was an aircraft mechanic for 21 years I wouldn't do it - not my expertise. But when I watch my guy do it (he's also a swiss-certified watchmaker) I have full confidence that what I'm getting back is going to be better because of his work, and it is.Disassembling a Leica for routine maintenance is an invasive procedure, possibly more damaging to the camera than using it without routine maintenance.
