Replace glass mounted third brake light in 2002 Bravada

I bought a replacement third brake light from an auto wrecker for my 2002 Bravda. Any tips on how to remove the old and put in the new? I
thought removing the screws (one from each side) of the lens housing and it would come out nice and easy, but it looks like I may have to remove other parts.
Any thoughts or suggestions?
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