GMail does have an import feature. You will need to deal with all your accounts that use your earthlink account and have those changed along with any other users you want to continue corresponding with. arthlink should allow forwarding and if you keep that account for a bit, you can respond to any correspondance with your gmail account.
Good luck. I've advocated gmail, yahoo mail, etc. over provider accounts for may years. Loose your provider and you loose your mail account. Gmail will work on any provider's network.