The Dacor is not the easiest DH to start on, there are no reproduction parts and few NOS ones around. I have never dove one but from what I hear, they are not the best of the bunch. On disassembly, there is no need to take the HP diaphragm apart unless you plan to make a new one. By doing so, you introduce more chance of destroying it and there is nothing to gain from dissembling it. The replacements come as a complete unit. Another possible problem area is setting the lever height. I have not rebuilt a Dacor but if it's like all the other DH regs I have restored, lever height is critical to proper operation. I have one in the works to rebuild sometime this winter along with a Nemrod.
If you intend to dive it, you will want to replace the hoses. The 1 inch on both end variety like the Dacor uses are not too common. IMO, a better alternative -if you don't mind mixing brands- is to use the reproduction USD hoses and mouthpieces. Actually I prefer the reproduction Voit mouthpieces for diving, those are what I use on my "I don't care if it don't match, I want the best diving DH " regs, otherwise the curved USD ones are in close second place for comfort.
On a related note, if you have never dove DH regs, they are different beast. To get the best out of them, they have to be placed properly. Sticking them on a modern BC, be it a jacket style or BP/wing will not get the best out of them and you will not like the way they dive. There have been several threads on the subject over the last few years, both here and on VDH.
