@Mnemonic I have never personally used one of these cos i cant really afford it. Also as far as i know they will replace the modem cos its part of the contract.
Also i would imagine that (if im correct) the router would have a web interface.Not all do but some of them do. If this is a case , then i think it would be easy enough to write a custom brute forcer or use any know web based brute forcer