It should be just a bulb. take a small flat blade screwdriver and look on the sides of the clearance light for an indent or something to allow you to pop the lens off. Sometimes there is no indent and you just need to pry the side up. After the lens is off the bulb should pull straight out.
The bulb number is probably printed on it. If not just take the bulb with you to the auto parts store and match it up.
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2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup