Too bad I didn't see this thread earlier... I love networking!
here are my opinions on the project, sorry if I repeat anything:
That layout is exactly what I helped install at a local coffee shop for their free customer internet access. (minus a couple switches in certain places.) It's been up for a year, still working, so you should be fine. I think the kind of jacks you push the cable down into are less permanent though. Pulling on the cable from the reverse side would yank the wire out.
Get a Linksys router! Or maybe a Netgear. I got a router that wasn't Linksys (it was SOHOWare) and it gave me ENDLESS grief! I'm talking stuff like responding to WAN side dhcp requests, and attempting to broadcast packets on the WAN side using ip address 0.0.0.0. My net admin a few years back had to come to my room and unplug the thing while I was gone, because it was kicking other people in my building off their connections. There are also Linksys routers you can buy, where you can plug your printer into the router, and all computers on the network can print to it without any one computer having to be on all the time.
There are ethernet jacks that don't require punchdown tools. All you do is strip the wires in the cat5, curl them under phillips screw heads, and tighten them down. There are also jacks that are completely enclosed in a plastic box, and that plastic box just sticks to a wall using double-stick tape. (you could use those pull-remove 3M foam tapes too.) but it wouldn't look as professional as a wall jack.
I recommend using a higher grade than cat5. Get cat5e, or cat6, if you can. I frequently see them for the same price as cat5, and while cat5 will get a connection just fine over long cable lengths, I think you'll get less packet loss with cat5e and cat6, and you'll be able to plug a gigabit ethernet card in later without upgrades. (that would mean being able to do things like virus scan a computer across the network, watch a DVD that has been stored on another comp's hard drive, or put your noisy drives in a different room so your main computer stays quieter.)
I've seen jacks that came with insulated enclosures and jacks that didn't. You do need something to protect the contacts in the jack from whatever falls down between your walls, but I think most of the wall-mount ethernet jacks fit into the same kind of metal enclosure as light switches and electrical outlets. You might use a caulk or putty filler of some kind around the holes, because the one jack in the coffee shop that was in one of those metal enclosures stopped working after a few months. I suspect something fell down and shorted a contact and did something to the router's port it was plugged into, because that jack wouldn't work on that port after that - only other ports. A hub worked on the weird port though, and that's still running.
The plastic brackets you need for cable mounting are called "cable staples" at Lowe's. It's a little finishing nail with a plastic U attached to it. If you have any cable running on the outside of the walls, you can also get a cable conduit you can run the cable through and stick to the wall, and paint to match colors.