I modded two Novatouch keyboards (45-55g dome mods and dental rings).
It's all been said above - it is a matter of practice and paying attention to details.
Opening keyboard is easy, but you need to keep an eye on domes so they won't jump up and all springs go all over the place. If it happens, you can still put them all together, but its just more work for you;)
You need to slowly pull apart top and bottom, so all domes sheet stays on pcb. From that moment, its all easy peasy:)
Pushing out stems and putting rings on them and back in the frame.
I paid £2 for dental rings. So yes, it is not worth paying $100 for silenced keyboard, if you can do it for cheaper.
However, if you have rather clumsy hands and not really good with handing small objects etc then you would better pay for type S.