The best advice is don't bin the window$ until you are happy with the linux basic's, that way, if, like me, you manage to screw it up, then you can at least boot back into window$ to get advice and suggestions.
Oh and the other bit of advice is to bin the usb modem. I found the speedtouch that I had, to work ok once I got it configured, but it used to annoy me when swapping between OS's, the delays etc and also, every now and again, I would get a snag that no one knew how to fix (line 150 speedtouch.sh missing, etc, etc, etc - I won't bore you with the lot), and the only cure was to re-install the OS, and that got me back to square one.
If you have a look here
you will get some idea of the various solutions to adsl connections (I went for a SAR110
and haven't looked back> VVV happy with it.)
Anyhow, all the info you need to configure it is here
though you should probably print it off and then follow it through. It looks pretty much similar to how I had to do my speedtouch (when I was still using it).
Give it a go and if you still have snags, then check back.
p.s. I think this is straight forward - my linux knowledge is pretty minimal as well - I'm a truck driver
pps. and if you double post like you have in the newbie and hardware forums, you will probably get a "snottygram" from one of the moderators - it's "frowned upon"!