What does nic_install really do?

In search of understanding exactly what I need to do to my TiVo (and how I screwed it up earlier this week), I would like to understand exactly what nic_install does under the hood. I was unable to find any clear documentation but the following features seem to be mentioned or implied in different places.

1. Installs drivers for various network cards (TurboNet, AirNet, CacheCARD).

2. Disables or mucks with initrd in some way to prevent hack overwriting.

3. Installs and runs on boot the ftp, ping, and telnet services.

Is this accurate? Have I missed anything?

Thanks,
Scott