how do i go about becoming a judge for our local comic shop? we need to get one for the dci points and map packs.

There are absolutely no requirements to become a "judge" for SWM or any other WotC game except for Magic: the Gathering. How you become a DCI-sanctioned venue is another question entirely. Go to the Wizards site and at the top there is a pulldown menu called "events" in that menu is a link to the DCI site; follow the appropriate links to become sanctioned.