The network card is call a TurboNet card. I got the card from a seller on eBay for about $50 and installed it in my Tivo last Saturday night. The installation of the card and software pretty easy. The card has a female PCI slot on it that fits on a male connector on the edge of the Tivo motherboard. There is a RJ45 jack on the card that take the end of your network cable.
From that point you can use your network connection to get the program guide data over the internet. The Tivo 3.0 software has drivers for the TurboNet card and support for broadband updates natively. If someone has a dead modem, they could just buy a TurboNet card and throw it in the Tivo. Then set the dialing prefix to ,#401 and it is done. You don't have to remove the hard drive.
Of course I had to go a little bit further, so I removed the Tivo hard drive, booted to a linux install CD and installed some software on it using a PC, but it is really straightforward and well documented. The software install installs drivers for the card and support so that you can ftp files to and from your Tivo and get a bash prompt via telnet from your Tivo.
I put the drive back into the Tivo and restarted it. Then I installed Tivo Web. I can log into my Tivo from anywhere on the internet and do almost every Tivo function from a browser. The Tivo Web essentially turns your Tivo into a web server. You setup the IP and port number for the web server to listen on and then set a username and password for the site.
It is a really nice interface that allows you to search for and set recordings from anywhere on the internet. Using the Tivo Web interface you can schedule recording and search for shows while you are watching something from Tivo. So it's like you can navigate the menus behind the scenes. The interface looks really great using Mozilla, but not as good with IE though viewable.
Another cool thing is that a bunch of guys are writing new scripts (in TCL) to add functionality to Tivo Web. I loaded one yesterday called What's On that displays the Live TV Tivo Guide over the web.
Here are a few links to learn more installing the TurboNet card and installing Tivo Web and all the cool stuff that you can do with it...
TurboNet Card
Tivo Web Project
Installing Tivo Web Step by Step






