-drain the coolant
-fill with water and a coolant cleaner (follow cleaner instructions)
-drain, fill with distilled water, let run for 10-15 minutes
-drain, fill with distilled water, let run for 10-15 minutes again
-drain, fill with the proper coolant and a little bit of distilled water as needed to get your mix right (I recommend a coolant measuring tool, just a couple of bucks at your parts store, to make sure your mix is right)
Do this all in one day - Don't leave water in the Jeep overnight, do this in one day. Winter has arrived, and I would hate for your to freeze/crack your engine block. You don't have a location listed, but in Utah we are seeing freezing temps each night.
Capture all of your used coolant - don't let it drain on the ground as it is toxic to plants and animals. My local landfill takes coolant free of charge. Periodically, I swing by to drop off coolant/oil/transfluid/brake fluid/etc
The heater not working could be related to your incorrect coolant problem, but check other things as well. I am not sure how the system works on the newer grands...is there a heater valve that is stuck closed? I recently had that issue on my car (not even sure if your grand has a heater valve). The older grands (like my wj) suffer from broken interal parts called blend doors that block airflow from traveling past your heater core. Your grand is so new though...confused.
So...if you have the wrong coolant, you need to fix that ASAP. If that does not fix your heating issue, you may have other problems. If you do have some type of heater valve, it is possible that coolant that is suffering breakdowns or thickening issues could be gumming up the heater valve, heater core, or some other passage. Hopefully the coolant cleaner additivies will break that gunk down and get it out of your system.
*Project Yeti* 99 JGC Limited 4.7 w/6.5" Rockkrawler LA & IRO A-arm, Goodyear MTR 35's on MB TKO's, 4.56 Yukon's, Iceland Offroad Bumper/Flares/Sliders, Protofab Rear Carrier, SuperChips, Uniden/Firestick, Flowmaster, Smittybilt 8k Synthetic Line Winch.
My Jeep is Organic - Undercoated in 100% all natural Utah Dirt --- Utah Jeep Crew #49 ~Will
2012 JeepForum GCOTY --- Project Yeti Build Thread