Oooohh you... would have been much, much better off... simply buying one that already had that stuff... for a few dollars more
Prefer to do things the very very hard way, eh? Well here is the long and the short: You have a 2018 Compass, and the current year is what? 2017. So, just how much info do you think exists at this point in time? How far along do you think the aftermarkets are in developing stuff for this vehicle? The answer is not very much.
Aftermarket is slow, it will be some time before I would expect to see any significant offerings that are directly for the MP / new compass. Universal / custom fit is going to be the main option for now.
As for swapping radios and such, you are here looking around for pioneers with knowledge to share well here is news for you: YOU are the pioneer. Its a new car, in a brand new redesign. Nobody has had much of any chance yet to fiddle with modding these things. Most of us are not going to, either, because of warranty concerns and because most people don't want to screw up their brand new cars.
Its one thing when you buy a 10-year-old honda that thousands of people have poked and prodded and shared information on. You've got yourself a totally fresh designed SUV that nobody has seen before, much less taken apart, and you want the sky to open up and magically drop you some experts who have spent the time and the money, and know exactly what radios and part numbers you should look for and what hiccups and challenges you face doing a swap? Sorry, those people don't exist yet. YOU are going to be one of those people, maybe, if you have it in you. If you can't figure out some things for yourself and do some experimentation without the help of a how-to guide then you are just going to have to wait and use your SUV as-is.
You are really screwed with regard to the radio, depending on your options. On mine, a lot of stuff is grafted into the 8.4 inch screen such as controls for the heated seats and wheel and display of the currently selected temperature and fan settings. I don't know about your 5 inch radio, but mine, its pretty difficult to imagine how you would replace a head unit that controls the majority of the HVAC system and the auxiliary features.
You apparently don't realize how much more intertwined infotainment systems are with the rest of the car nowadays. Sure, in the old days the radio was a mostly independent piece, it had wires merely for power, speakers, and not much else. Now, there is steering wheel controls and HVAC settings and feature controls in there, you don't just up and replace that. Not in mine, anyways. Certainly not with aftermarket. And, although not many people have had a chance to toy with these units yet, one would think programming would be fairly specific from vehicle to vehicle so I'd be surprised if you could just order up the larger head unit and drop it in and have it all magically work. What if the wiring harness plugs don't match up?
Boy you really have an uphill battle. If you are clever and handy with a soldering iron, have a few bucks to spend and some hours to put into it, you could be the first. If you are waiting for someone to say "well you just punch these exact part numbers into moparpartsonline and do this this and that" you are screwed at this point in time.
So thats basically it, the options are
1) Figure it out yourself. (at risk of totally wrecking something if you don't know what you are doing)
2) Wait however many years until someone smarter figures it out.
3) Run back to your dealership and tell them you changed your mind and want to fork over some more money for a better equipped model.
Sorry if I come off as cranky about the whole thing but me personally I always shake my head at people who buy a BRAND NEW PERFECTLY GOOD CAR where everything works as designed and before they even get it home they want to rip it apart and start messing with it because somehow its not good enough as is. Why even buy it if it isn't everything that you wanted?
But anyways, sorry to be such a sourpuss thats just my two cents.