I don't have a diagram, but I've swapped the bulbs in both jeeps. Do you mean the dome in the sound bar? The plastic cover is attached with two hook arms at the front side of the jeep, and opens down at the rear. You can open placing your fingers on the rear, and squeezing back and down. I also used a small flathead screw driver to gently pry it open.
Be sure to let the bulbs cool, or use a towel to get the bulbs out as they get hot fast.