How do you replace third or 'high' tail light bulb on a 1994 suzuki sidekick 4 door?

First, there is no need to remove the light's housing from the rear door. On either side of the housing there are plastic clips that look like two circles, one inside the other. Take a screwdriver (or punch or anything like that) and push in inner circle of the clip. Is will sink in about a quarter of an inch and loosen the clip. Use your fingernails to pull out the clips. With the clips removed the rear housing will pull straight off. Remove the housing then remove and replace the bulb. To reinstall the housing make sure the center of the clips are pulled out about a quarter of an inch, reinstall the clips into the housing and push the center part in until it is flush with the rest of the clip. This will lock the housing in place.