If you do decide to go with a separate GPS unit, try here for the mount:
http://www.proclipusa.com/dashboard-...rban/2002.cmsv
I have the version for my 99 Suburban, and even though it looks like a permanent mount, it can be removed with no damage or holes in your truck

 

I have a Garmin with a 5" screen and I use a beanbag type of mount. I set it on the dash over the top glove box door. I like this way because when I get out of the car I can just sit it in the passenger footwell.

 

I have a small Garmin Nuvi unit which I can stick in any car that has a 12V plug. I has gotten me all over the country. It was $89 when I bought it. You can set it up many ways as to routing and avoidances like HOV lanes, dirt roads, toll roads. I have used the DETOUR function when I have encountered heavy traffic, which I seem to encounter in driving through Nashville when going in that direction as it is a day two morning for me and I hit rush hour. But you need to be familiar with your route when planning a trip to estimate when you could hit heavy traffic.

 

I'd rather use a dedicated GPS rather than my Galaxy S4. I currently have a Garmin Nuvi 50LM (lifetime maps) and it has been fine. Occasionally it will give a goofy route (Google Nav has done that too) but otherwise it's pretty accurate.