Welcome Bungle
A nice choice of car, not that we're biased around here or anything...
First mod I'd recommend immediately would be a DTUK Pedalbox which will make the car far more responsive and even the standard power output feels loads stronger with one of these fitted.
A difficult mod to explain to a sceptic but it just works, and works very well too. A must have in my book.
There's a dead inch or so of throttle pedal travel that this unit eliminates, not even a remap with revised throttle mapping can get around this due to the electronics in the pedal itself. The Pedalbox along with a remap or tuning box absolutely transforms the car.
Next up, remap wise you have plenty of choice. You're out of factory warranty now, give or take, otherwise I'd recommend a JB1 tuning box for its adjustability to alter the mapping.
REVO or APR are the immediate names that spring to mind that would come highly recommended. I'd go with either depending on the proximity and reputation of the nearest dealer.
If it's a manual gearbox then don't go too mad with the torque, the clutches on these cars aren't renowned for their ability to take much more torque than standard.
I've no idea on the ESC switch out but have a search over on golfmk7.com as the Americans like to experiment with these things and if it can be done via VCDS then someone will have figured it by now!
As for the nav unit. That's a bit of a minefield. You can get an add in dealer fit (you can buy them on eBay and self fit easily) kenwood Garmin module that will work with your existing head unit screen but you can't easily upgrade from the standard media system to a factory nav head unit. VW lock the unit to the car as there were literally thousands and thousands of previous generation nav units stolen as it was a popular retrofit in mk5 and mk6 Golfs; with the mk7 they've made it much more difficult to upgrade. Google "component protection" or search on here.
You can also get aftermarket units for the mk7 but they're £££.
