Installing Cab Clearance Lights

I would like to add a set of amber cab clearance lights to my 2000 GMC. But before I whip out the cordless drill and make holes in an otherwise perfectly good roof, I thought I would seek out the advice of others who previously installed these type of lights.

Any advice would be greatly appreciated plus I have three questions I definitely need help with.

1. What is the best way to seal the screw holes against water leakage. Silicone caulk?

2. What is the easiest way to get behind (or to remove) the headliner so the light wires can be routed to a connecting point? I do have the small factory roof pocket console with map lights and electronic rear view mirror.

3. Is any particular brand of clearance lights superior over another in terms of quality, durability and installation ease?

Many thanks in advance.
Joe