6.5's and even 6.75's will fit in the door just fine, just takes a very minor bit of tweaking, minimum making new mounting screw holes (self tappers or drilling new holes) and at the most some minor trimming of the speaker opening.
This is my door with 6.75" mids installed with no trimming just 4 new screw holes.
You should be able to add everything you want and still retain the SYNC system and factory HU in the truck but it will take some sort of a line out converter at the least and maybe a processor. I am not 100% up to date on factory integration but I can tell you there is just as much research to do on this topic alone as their is on the entire remainder of the system, ranging from a $20 line out converter up to $800+ processors and many products in the middle. It all depends on your final goals with the system, honestly a decent line out converter (LOC) should be all you need/want. I don't know if the factory system has a built in amplifier though, this would be part where you might want to consult the shop as their might need some bypass work necessary.
A very nice straight forward system with a decent budget (not cheap but not huge) could be something like this...
SPL2k box with a JL 13tw5
JL Audio HD900/5
Hertz HSK165's up front and just a pair of decent 6x8's in the rear
Then whatever it takes to get the audio signal from the factory HU to the amplifier.
Putting the tweeters into the sail panel I think you would run into separation issues, I have mine there and a good bit of time alignment (delay) to those speakers to keep it all in sync, but what you could do is experiment with location, get the tweeters wired up with some extra long wire and some double sided tape on the back side and then mount the tweeters up and see how you like it. You could also grab a tape measure and actually measure out the physical distance from the speakers to your listening position. If you are going to experiment then A-pillars is considered the most ideal location for the tweeters in these trucks followed by sail panels, then near to the mid in the door.
Components or seperates generally consist of a package of 2 speakers (per side) and an external crossover
1 side (mid, tweeter, and crossover)
while coaxials are your normal run of the mill car speaker, (this has a tweeter mounted in the center of the mid)
I believe those HV165's you were looking at are simply the Mid from the HSK165 component set
