Researching the Best Double-DIN In-Dash Navi

[alexabu]

Looking to upgrade stock Tahoe radio with a Navi, Looking for advice, if i should install my self, if i should install door speakers and subs at the same time if possible. Help me out.
Its a Black 08 Tahoe LS

 

[09Hoe]

I have just installed all those but the installer that did my car accidentally tap the anti-theft wire with the headunits acc wire and locked the engine so becareful! lol