mac address on a cisco 871

Hi.

i just bought a cisco 871W, because i wanted to play with something along with my ccna studies BUT.

i got a ISP who has been given me a cable modem, and is giving me a specific ip address via DHCP, my problem is now, how do i see which MAC address my new router have, so i can tell my ISP about the new mac address??? i know i can type:
ip address dhcp client-id Ethernet 1
but still, i dont know what the mac address is, or can i change it somehow???

awaiting gladly for an answer 🙂

/christian