I don't know if this is going to give you everything you want. But here is the published DNG specification:
Sorry, the link doesn't work. But that is where you can find it.
Let's try a different link. If you scroll down this page, you will find references to several PDF files that might provide you with some of the information you are looking for.
I can try to answer some of your basic questions.
I say that there is no discerable difference in an original NEF and a converted DNG. Others agrue that there is a "quality" difference in using a DNG opposed to the NEF.
When using Adobe Camera Raw--whether in the plugin for Photoshop, Bridge, etc. or in Lightroom--you should see no difference between the result you get for a NEF and a non-linearized DNG created from that NEF. When processed using the same develop settings, they should be identical. If you see a difference, we'd consider that a bug--please report it to us by posting sample files (NEF, DNG and the settings used).
I don't know if other raw converters will produce identical results for a NEF and DNG.
If the linearize (demosaiced) option was chosen when converting the NEF to DNG, the process of "developing" the DNG and NEF inside Camera Raw is slightly different. The NEF will be demosaiced on the fly, whereas the starting point for the linearized DNG is the demosaiced data that was created during conversion to DNG. I would not expect this to degrade the "quality" of the image, but if anyone has an example where it does create a qualitiative difference, I'd really like to have an example to investigate as a potential bug.
When you convert NEFs to DNG using the default options you should be getting non-linearized DNGs, not demosaiced DNGs.
...can someone at Adobe technically explain to me ...what if ANY changes in the original file occur.
Converting a NEF to DNG does not change the original NEF file at all.