This is exceedingly easy. Not foolproof but easy. Go buy Cat 5e wire (or Cat 6) buy a crimper and connectors. Follow the instructions in the box. Really it is easy. As for the modem / router most will self setup. Don't be afraid. You really can't break these things.
Are you doing any home automation (using the computer to turn on and off your lights or run security / heating / tv's)? We have a beginners system in the LA house and will go fully automated up north in the new build.
The house was prewired but... the prewire contractor only ran one cat 5 to my wifes office (everything is done home run to central spot. So the choice is use the one cat 5 for hardwired land line to support FAX at her office or use it for networking but you can't have both. Her office phone is a wireless unit. We have 9 phones working off the same base unit and a second system with 4 phones off a single base that is connected to a Magic Jack.
I don't think I want to do automation via a computer network. X10 protocol stuff would do everything I need, I think.
I went through 3 sets of wireless networking gear ever spiraling upward in cost and supposedly capability and NEVER got reliable connection between her office and mine (different floors about 1/2 a house away.) I even got a repeater and still no joy. I originally asked for power line modems at the local emporium of technical computer equipment sales (STAPLES) and no one knew what I was talking about which is what started me through the various wireless trials and tribulations. By the time I had tried all the wireless crap (OK the LInksys equipment is good stuff just not working for me) Staples was stocking powerline modems. I bought a couple and voilà we were networked. I use the LInksys wireless router as a wired router connecting my computer and DSL modem. Wife gets to internet via powerline modem to that router.
So now I bought a Dell Studio 16 laptop with built in wireless connectivity and wired network capability. It gets great signal strength (why not at 3 ft from the router) but won't talk over the network. Meanwhile I have a connectivity problem and get telephone tech help from my ISP who claims my DSL modem is bad. They have a new modem that is wired and wireless and will handle 3 computers for $100 ($50 after rebate) so I order one. The next morning without two women's voices buzzing in my head (I suppose I'm sexist but I usually get better help from a dude) I power down everything at my computer and reboot everything only to find that the DSL modem now works perfectly. Oh well... I don't mind the upgrade to wired and wireless DSL. I'll keep the wired DSL modem and the Linksys wired and wireless router for just in case as a backup in case of hardware problems with the new modem at some future date.
I make no claim to being particularly good at computer networking and have repetitively demonstrated that lacking but I'm not completely incompetent having some rather wide applicable experience and credentials (I have made a living as an electronic instrument designer, most importantly medical electronics including dual beam ultraviolet spectrophotometers for blood analysis and I retired as a computer scientist with a BS degree in computer science, 1984 and a MS in software engineering, 1986.) I'm feeling the increasing pinch of obsolescence as time passes and more and more I find myself identifying with my previous incarnation (Physicist (1972) and my last one (MS Instructional Technology 1994.)
Yeah, yeah, I know it looks like I couldn't hold a job or had a short attention span but I like to think I was versatile. Anyway, sometimes there is more than meets the eye with the supposedly plug and play. If I can't get the whole shebang up and running to my satisfaction with the new wired and wireless DSL I will not worry a bit. I'll just throw a little money at some technogeek working for minimum wage at a computer sales store, offering a bonus when the system is up and running. Either that or find some 12-15 year old whose mom will let the kid get paid $50-100 to make it work.
How does this relate to earth sheltered homes. Well... with sufficient rebar in all walls and ceilings and sufficient earth cover your wireless signal will not radiate sufficiently to enable anyone to piggyback (pirate your signal parasitically.)
Pat