Drilling through brick fireplace-Gas Logs

Hello (note:I seem to be having posting problems, so excuse me if this shows up twice)

I am installing gas logs in a 1960s era brick fireplace, and would like advice on drilling through the firebrick and outside brick chimmney.

I'm planning to rent a hammer drill and masonry bit, and will follow all requirements from the gas log manufacturer (I don't actually have the logs yet).

Questions:

1. is the angle I drill through the fireplace important, or can I just drill horizontally from the firebox to the outside of the chimney?

1. I'm planning on putting the gas access hole in the back corner of the firebox, near the floor of the firebox to avoid overheating. Is this the best location? (there's no ash dump; firebox is about

1. can I seal the hole around the gas line by filling it with silicone from the outside?

2. I've never drilled through firebrick or brick before, so any advice to keep from damaging the surrounding brick would be appreciated.

Thank you for any advice! DanH