I've installed cab lights on a few 2nd gens. Although it was on 2nd gens the process would be virtually the same.
1. Drop the forward portion of your headliner enough to fit your arm in (you'll have to remove your HUD)
2. Remove your pillar covers
3. Arrange the lights how you want them to sit and trace them with something that's not permanent or damaging to your paint (map pen, pencil, etc.)
4. Also mark where the mounting screws and wire(s) will go through.
5. Drill small pilot holes for the mounting screws and a big enough hole for the wire(s)
6. Apply a small bead of chalking around the holes (as close to the holes as possible. this will avoid the chalk from mushing out the sides of the light)
7. Mount the lights
Now to the actual wiring
Note: all the aftermarket cab lights I've installed only had a power wire because it grounded to the mounting screws.
1. Find your power source. (I connected mine to the parking light wire in the headlight switch. So when my parking lights come on so does my cab lights. I've seen others run an independent separate switch but that is ghetto. I recommend you find a headlight wiring diagram but you can always use the process of elimination)
2. Connect the power wire to the power source.
3. Find a good place to run the wire from the power source to the the underside of your roof. (I ran through the dash, up the driver side pillar, and on top of the headliner)
4. Use T-connectors to tap the wire from the lights into the power wire. (I highly recommend capping and then taping off the end of the power wire. Some people don't and then it ends up grounding out)
5. Double check all your connections and test the lights.
6. Now time to put your truck back together, clean up, and enjoy your new lights.
I hope this helped. If you have any additional questions feel free to PM or email me.
2000 Dodge Ram 1500 Sport 4x4 - 5" lift, 36" tires, CIA, exhaust, CB radio, bed liner, undercoated, and more
2006 Dodge Ram 3500 Laramie 4x4 - trans temp, EGT, boost gauges, 5" exhaust, CIA, Fass 95GPH