You should be able to use the router features of the 7500, of course you will need a cable modem since the 7500 contains a dsl modem that will not function for cable.
Connect the Ethernet cable from the cable modem to the E1/uplink port on the 7500, which you should configure for the WAN uplink mode in the configuration pages of the 7500 -- see your manual for details on how to configure it.