My suggestions fall along the lines of security. You might want to consider hardening the router that you get. Depending on what you end up with, some might allow you into the guts more than others, this is true of the Cisco DSL Modem that I use at home. On top of this, you might add in the firewall rules on the linux box, further isolating your internal network with by a DMZ. Also, your boxen is only as secure as you make it. I would strongly recommend reading up on various procedures you can implement to strengthen your boxes. Practical Unix & Internet Security from O'Reilly is a pretty good resource. If you are just learning Linux (and it sounds like you are), I would recommend being overly cautious and not turning anything on (or installing it even) if you are uncertain what it is doing (although sometimes that is hard to do). Also, if you use Wireless, you might look at restricting access based on MAC/Ethernet addresses, so you don't get a bad-guy getting in that way. In short, be a paranoid penguin ;-)
I'm not a security expert, but I've just done a bit of reading on the subject and am very conscious of it with my job.

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"Ex libris un peut de tout"