Are there any installation guides on dash cam installs for 3rd gen, 2008 specifically? Everything I can find on Youtube are 2015+. I'd imagine mounting it to the rear view mirror and grabbing power from the overhead console would be the way to go?

 

I bought a hard wire kit from spy tech for $10. It comes with a fused wiring harness and mini usb connector that plugs into the dash cam. I was getting radio interference with the receptable plug. the hard wire kit fixed it.

the overhead console power supply for my 2500 2007 hook up was constant power. You can use that but you would have to manually shut it off each time or the battery would go dead. I wanted a power source that was powered only at key on...this way it turns on and off with the vehicle. the easiest source for me was at the tipm. I used a fuse tap into a fuse location that was non-essential...so if it blew the fuse I wouldn't lose abs/pcm etc.
I ran the fused wire from the tipm, into the cab, up the a-pillar trim cover, under the headliner to the mirror. the grd wire you can screw into any metal part of the interior...I found an existing grd screw and used that.

 

The dash cam you'll buy or you've bought should offer a hard wire kit to plug directly into the fuse box.
Their are also generic hard wire cables as well.

Installing a dash cam is not rocket science, you'll figure it out.