2001 Pathfinder LE stero/climate replacement.

[Desert-Fox]

Hey guys,

First some background information of the vehicle:
-It is a 2001 Nissan Pathfinder LE.
-It has the GPS and the original headunit.
-The headunit and speakers are from the BOSE upgrade, nothing has been replaced.
-It has steering wheel controls(Important for new headunits...).
-It has the VHS player in the very back, with the flip down monitor for the rear seats.


As what seems typical of the 2001 Pathfinders with navigation, a few of my buttons have popped off. Due to being a perfectionist and insisting on having my stuff work 100% properly, I'd really like to replace the system with something that is updated and will work more efficiently.
As for my course of action, I was looking to install the auto-climate control from a Pathfinder without navigation. Additionally, I'll probably put in a new touchscreen navigation/radio.
For the radio/navi, I was looking at the Clarion VX400 or something along those lines. It doesn't have to have GPS, but it is plus if it does. If you have a recommendation for one, feel free to lay it on me, as I have no clue what is out there to be honest. And I'd like something that would work with my OEM steering wheel controls.. This thing may be used?
So my question is, are there any laid out guides for doing this? I've seen people doing this, but haven't gotten a really strong feel for what exactly was going on...

Also, while on the topic, at some point I'll probably replace the Bose speakers.. Is there a way to use the Bose wiring harness with new speakers, or would it be much easier to just run wire from the headunit to the new speakers?

Thanks!