Most of what you need to know is on my web site.
One thing to keep in mind when working on high end vehicles, is the sound proofing; it's everywhere! This makes things extra difficult with respect to finding holes through the firewall. In the last couple of years, I've come to the conclusion that it is always best to drill one just exactly (or close) to where you need it.
For example, Honda has always had at least one unused hole. Nowadays, it is too far to the right, which means wires get snaked in and around items which make threading difficult, and this often places the wire in harms way. All future installs I do will have a drilled hole for the power.
Antenna holes are a hotly debated item, and you have to decide just how dedicated you are to mobile operation. If you are, you'll drill holes.