ok, this may sound rude, but I am not trying to be. I get alot of guys here that are told lies and can never get it to work. let me be clear, if you are banned from xbox live, changing your ip will not help. if someone told you that, they are a liar.
Comcast who you clearly state you use, by default uses a static public ip address for its customers. this means the public address (74.104.88.xxx) will never change. I can track it hee on my end, (its part of being admin LOL) Our log will only let me go as far back as april first, and since then your ip has never changed. looking at your profile, it appears you have used a pc in 4 other locations to sign into acidmods. but the one you primaraly use is the 74.104.88.xxx If your public ip address ever did change it would be VERY similar to 74.104.88.xxx, this is because it would be ranged. this is how the FBI or other law enfocment can make sure your not selling kid porn. think about it if people could just change the public ip address at will, how could you ever track it?
The techs you are speaking to who are telling you to reset the system, or do ipconfig, etc they are changing your PUBLIC ip address which I would guess with a dlink is somtething like 192.168.2.xxx (linksys systems by default are 192.168.1.xxx) these numbers you can change, but it will do you no good, these numbers are only seen by your pc and the router, or other pc's on your network.
you need to deal with the spammers, or buy a unbanned xbox, whatever it takes to DEAL with the problem, not run from it. If you want to have a real discussion on why you want this changed, I will be here but I need the truth to help you.