docsis 3.0

My internet provider (xfinity/comcast) has been very persistent & insistent that I need to upgrade my cable modem to DOCSIS 3.0. What does this mean? Will my old wireless 'G' router need upgrading too? Have only internet ... no cable TV or phone service. Thanks

For Sale: Payment: Paypal. Alternative Payments: I will also take Facebook debit payments (no fees heh) or USPS money orders. Shipping Method: USPS Priority or FedEx Home Delivery Price: Prices are OBO, so make me an offer. Reference: Heatware is wolfofone. Other: Continental US Only...