The brake light bulb has been out on my 3rd brake light for awhile. Being my truck is coming up for its inspection I decided to replace it last night. I didn't think it was going to take me 2 days to do what should have been a very simple fix.
After removing the 2 fastener screws I had to pry it away from the cab/roof! Yes, I had to PRY it! Back when my truck was under warranty I noticed water was leaking around the inside of the rear window. I took it to the dealer and they subbed the repair out to a local glass company. What they did was retain the factory POS gasket and siliconed the sh** out of it and put it back together. What started out as a simple bulb replacement at 4 pm yesterday until 8:30 last night turned into a completed job after 1-1/2 hours this morning.
I went through 3 scotch brite pads, 2 pot scrubber pads, a whole 16 oz bottle of alcohol, 2.5' of 1/4" thick X 1/2" wide insulation tape, 7 shop towels, a roll of paper towels, and 2 tubes of industrial clear silicone caulk. Oh, and 3 new Sylvania Long Life #912 bulbs.
Let's just say that the next time any of the 3rd brake light bulbs go out and I need to replace them I will need a whole new light!

 

I siliconed mine too and thought I had it licked but just noticed the other day that it still leaks a little. I had bought a new one ($80 on ebay) but didn't use it. I did keep it though, so now I get to put it on. Of course, I'm going to have to pry the old one up and clean up the RTV like you did. I thought about that when I did it but I also thought it would be some time before I had to do it, not 60 days.

 

Mine wouldn't have been that hard to remove had they used a clear type silicone instead of that black toxic "must be removed with a pry bar" type of silicone! I have used it before and that's some bad a** silicone!
I wish I could have ordered a new one from online but I just couldn't see wasting the money on something I knew I could have cleaned up and fixed. But, as of yesterday, I started a "Saving Money For A New 3rd Brake Light" fund. And, it will come complete with a new and improved gasket design along with LED lights.