If you are a typical residential customer with dynamically assigned IP addresses, the best you can hope for is maybe a change in the last two sets of numbers if you turn the modem off for a long time. If you are a business customer with a static IP address, you could contact Comcast and ask them what range you have for getting a different static IP address.
Changing DNS records for any domain that you own or control will not change the IP address of your servers. Using VPN through a proxy server located at the desired IP address may work.
The Comcast router in the central office at the other end of your cable is the Gateway. If you you manually change your gateway settings, you will most likely no longer have a working Internet connection to anywhere.
EDIT: Maybe you should tell us what you are trying to accomplish by getting a new public IP address.
Changing DNS records for any domain that you own or control will not change the IP address of your servers. Using VPN through a proxy server located at the desired IP address may work.
The Comcast router in the central office at the other end of your cable is the Gateway. If you you manually change your gateway settings, you will most likely no longer have a working Internet connection to anywhere.
EDIT: Maybe you should tell us what you are trying to accomplish by getting a new public IP address.