Casey, you have all that stuff in the tutorials and lessons of the FSX "Ausbildungszentrum", don'T know how they call it in the English version. All the theory you ask for: all instruments explained. Flaps, Flight phases and how to run them and and what to do then. Navigation. GPS. IFR instruments, glass cockpits. I just have checked it, it is all there, with pictures and explanations.
That is much better than walls of text written by me and others, without graphics and pictures.
Check that "training centre", as it may be called in the english version. It's all there.
My point earlier was just this:; if you want to go indepth with a plane, don'T waste time with the FSX toys, their system depth is - almost non-existent. Pick one addon plane and then use that for a solid time to come, and get into it, in detail, that is more rewarding. Go with something of small or medium size first, and in half a year or so, when you got the experience, still have the interest and may have the money, get an airliner.
The Cheyenne can be ordered with 20% lower price currently. I have yesterday placed my order for the FSX version of it myself, I miss it from my FS9 times. Until 25th or 26th.
http://en.shop.aerosoft.com/eshop.ph...design=DEFAULT
But see if Aeroshop runs an American shop as well, I think they do, at least did.
Really, if you want to
dive into things with FSX,
then do it right 
: get one first addon plane small to medium size and start with that. And much later, when it is opportune for you, get one heavy bird. There are good reasons why people are willing to pay money on such addons and ignore the default planes.
They just don't compare. When it comes to autopilots and airliner FMS (flight management systems) at the latest - there is where a wide, wide abyss opens between the default planes and a quality addon. You'd be surprised how far a quality addon can move beyond what you believed you knew after having done the default equivalent only.
Hope I do not sound too missionizing. I'd prefer the term "enthusiasm".