i can guarantee setting up a router is going to be just as easy as any PCI DSL bridge, if not easier. with most ISPs, you can just plug the router into the DSL bridge, and then plug your computer(s) into the router, and you're set. forward a few ports so file transfers will work right, and you'll rarely even notice the router is there at all... until you see the madly blinking lights on the internet side, with nothing blinking on the LAN side, indicating another IIS or Windows virus is hammering away at the router (entirely ineffectually), while you're safely tucked behind it
also, you could be nice and just share the connection with your gf anyways. when i was living at home, i let my parents use my DSL even though they didn't pay me for it. they hardly use any of the bandwidth, so it's a convenience for them to not have to dial up, and have web pages and e-mail load faster, and as far as i see it, it's more networking experience for me (although i could set it up in my sleep with both hands tied behind my back).
regarding wireless, i would actually advise
against it unless you
need it. in addition to often being a pain to set up, you also open your LAN to passers-by. any wardriver with a laptop can pick up that you've got a wireless node, then it's a matter of time before they crack the WEP (wireless encryption protocol), and then they have free reign of your LAN, and free use of your broadband connection. furthermore, if you don't tighten it down enough to keep average joe llama out, he might connect to it just to check his e-mail or something, while unwittingly broadcasting a virus across your LAN where the firewall can't protect against it.
as far as routers go, a BEFSRx1 would be my first recommendation. like phoenix, i have the BEFSR41... it's relatively ancient, but it's ?ber-stable (i usually need to reboot it about once every 4-6 months), easy to configure, and efficient. if you want more ports (say you plan to host a LAN party), there's the BEFSR81, which is the same unit, but with 8 LAN ports. there is also the BEFSRU31, which has three ethernet ports and a USB port. while normally i wouldn't recommend an internet connection via USB, this might be a valid option for connecting your girlfriend's computer, as it doesn't require you to install a network card in her computer, but simply hook up a USB cable. if you don't want to share the connection, you can still get the protection of a linksys firewall with the BEFSR11, which is the same as the BEFSR41, except it only has one LAN port, which you would then connect to your computer.
in terms of pricing, i just checked amazon.co.uk, and here ya go:
BEFSR11: ?40.89 (wtf? why not just get the 4port model and have the expandability)
BEFSR41: ?40.89
BEFSR81: ?71.68
they didn't seem to have the BEFSRU31 at amazon.co.uk, however, i found it at dsl-warehouse.co.uk, for ?79.99
well there's a little info for you to start with
once again, i would strongly recommend getting an external DSL bridge and an ethernet card (if you don't already have one) over getting a PCI bridge. it just gives you a lot more flexibility and options. also, if the bridge dies for whatever reason, it's a lot easier to replace, and you don't have to install new drivers when you put the new one in (even if you return the bridge to the manufacturer, they may replace it with a newer model, which, with a PCI bridge, would most likely require new drivers).
if you do decide to go with the external setup, i'll be around to help you set it up if you're having any troubles - it's what i do