[MrClean]

Brian I have that exact same humi, the seal around the lid seem pretty good on mine. But the glass and hydrometer need sealing (on mine they were bad).
The hydrometer should come out easily by pushing on it from the inside. Just run a bead of silicone around it and pop it back it.
The glass was a little more tedious. The four pieces of cedar that butt up against the glass, I removed those with a pair of pliers (I put a clean shop rag over the wood so I wouldn't damage/mar it). They are held in with little brad nails. The glass will have a couple of spots of silicone on it, it wasn't easy to get loose, but it's tough glass. I just cut away what silicone I could get to, closed the lid and pushed down on the glass, it'll come out.
Run a good bead of silicone all the way around the inside lip (where the glass sits). At this point I let mine sit for 3 days so the silicone could cure and the smell dissipate. I have a brad nailer so putting the wooden strips back in was easy, you could glue them I suppose.
If you don't want to take the lid apart, the only option would be to silicone it from the outside, which for me, wouldn't look as nice.

Good luck brother!