Just dive in an offer to help and you will be in and running. The guild I belong to has over 300 members and some are just there to enjoy the sight and sounds. Others really dig in and make the guild flow. Once they know you are willing to help and participate they will be more than glad to have you. They know that some just want to watch and that is ok as well. Enjoy it, you will meet lots of wonderful people. If you meet one bad apple, so be it, there's many more wonderful people.