Changing email addresses is a pain in the butt. If you're semi-tech-savvy, I can't recommend enough getting your own domain name, and paying for an email service that supports custom domains (e.g., fastmail.com). This way, you avoid having this problem again if, for example, gmail goes under or you just want to switch to another email provider. If you'll be ripping this band-aid off anyway, switching from one gmail address to another, it may make sense to do it with a bit more resilience in mind.
As others have mentioned, I think forwarding is your best strategy. Just forward <oldemailaddress@gmail.com> to <newemailaddress@whatever.com>, and don't worry about updating anything. You'll still get emails from, e.g., the MMM forums just fine. And as people email you, you'll respond from your new address, solving the problem of updating contacts kind of naturally over time. The lazy approach!