Being an introvert myself, I do understand how you feel. I would suggest that you get in touch with someone from the guild via email if that is an option. I used to handle membership duties for my spinning and weaving guild. If a new member got in touch with me before a meeting, I could make sure to meet her at the door to welcome her and find someone at the meeting who shared her crafting interests - we have spinners, weavers, quilters, knitters, etc... and there was always someone who was happy to make the guest feel welcome.
Don't let your nervousness keep you away from a group of people who more than likely feel like old friends by the end of the meeting.