Hi, I been lurking on the forum for quite some time but been learning rather than posting. I have this head unit
https://goo.gl/KKn1Jo Joying 7" Android head unit from carjoying.com
It is installed with reversing camera, steering wheels controls (non-bluetooth type, but can be programmed for phone controls). Everything works and I've been very happy with it. The picture on the web page is actually showing it installed in a D40 Navara the same as mine.
There was a previous review posted by a member here:
http://www.navara.asia/showthread.php?t=32220 that has a similar unit. I have only ever installed factory firmware and not experienced any issues with the steering wheels controls not working or bluetooth audio quality (I only use the integrated mic in the head unit itself, not the supplied external).
Being an Android unit you can use whatever Satnav you like, TomTom works brilliantly on it and is integrated with the GPS hardware button and sound mixing functions of the unit. Google Maps gives you the added option setting destinations by voice control which is pretty good. You can download the manual for this unit from carjoying.com, and there is plenty of support on the web for this head unit.
There is a later model with Android 5.1.1 slightly cheaper which might be worth looking at. The upgrade for me (hardware) is only $35 from Joying but I haven't bothered at this stage.
If there is anything specific you want to know please ask.