Truly, NAV won't be hard and neither will the remote start.
Are you a do it yourselfer? If so, the NAV is easy. You can get the head unit, receiver and antenna off eBay and put it in yourself.
MOPAR has a great remote start system you can get from your dealer.
The seat heat option will require some wiring and switches to the console but it can be done. We added seat heat to a Magnum SRT8 this year with the factory parts.
Nothing is impossible...you just gotta decide how much you wanna spend.