I don't know who makes your 3G router but I saw company X with a ton of reboxed recertified 3G routers for $49, but I don't know the requirements.
First, simply look up your model number and its requirements.
I have an Acer One and have used 20 different versions of Linux YLMF (Just like a copy of XP, and works so great), KXSTUDIO Puppy Linux, SLAMPPP (Be careful with SLAMPP; it's loaded with all types of web servers and all or 90% of them are open by default, but a great system for those that want to have a great server but don't want to install all the different programs. I like the way Slampp uses the CUPS printing system. They have version 4.x and it has nearly ever printer driver ever made pre-installed) plus Puppy Linux, Partition Magic (Great for working on a Windows machine that died), Damn Small Linux, Slax Linux and Mandrake's new version (I can't remember the name).
I have six more on my keychain, but they are at the other end of the house and I'm tired but the point is, the little old Acer Aspire One will handle a lot; I even have Windows 7 on one. It's slow as heck but lets me get some things done that the other OSs will not, so I put up with it.