im adding some Hella lights up front. I am somewhat new to mods and general electrical work on vehicles. When utilizing the factory grommit on the driver side firewall is it easier to undo the tape and try and slide a wire through with the factory wires? Should I drill a hole and add my own grommit? Or can i poke a hole in the factory grommit and just silicone the hole afterwards? Will any of this void my warranty?

Just poke a hole and then silicone it. That is by far the easiest. Just be sure you dont nick the other wires and your waranty will be fine.

What I did was just punch through the grommit with a philips screwdriver...it makes a very tight hole that you can put a wire through, but is still tight enough to not let water/dust through. This way you can leave the old wiring alone. I wouldn't worry about warranty issues, it's just a poke through rubber. If you're worried about it, you can always slide the wire out and hide it before you take it in ...and if you do it like I did, the hole is not noticeable once the wire's because it's so small.

EDIT: when I say screwdriver, I mean a pretty small one...something small enough to puncture the rubber, and not too big so the hole is tight around the wire.

Thats what I did for my stereo wires

lol