I would concur that noise reduction should, in most instances, be applied somewhere at the start of a workflow rather than at the end of it, especially if sharpening will be performed. Generally, applying sharpening before noise reduction will just exacerbate noise and cause it to really stand out and make it hard to remove. From my personal experiences anyway.
The Nik collection (which is a free download from Google) contains a noise reduction module (Define) which I have had pretty good luck with.
Great tut Simone and thanks so much for putting it out there for us to play with. Here is my effort. If I have some time later on I might revisit and tweak parts of it to see if I can get a better effect that what I ended up with. Yours and Helen's images are fab!