No posted instructions that I know of, though you can search the internet and find various approaches people have taken.

Generally windows leak through the screw holes, though if not well sealed originally they can leak anywhere. The cabin top flexes a lot when walked on and will break the seal for the windows. If the windows are in very good shape and seem well sealed you can try removing offending screws, sealing them with silicone, and replacing them.

To re-bed the windows they must be removed, all old sealant carefully cleaned from boat and windows (difficult as you should avoid using acetone or solvents to clean the boat or windows), and then resealed. It may be a good time to replace them--if you take the old windows to Tap Plastics they will fabricate new windows for a very reasonable price. Have them drill the screw holes also (oversize to allow for expansion), as drilling through lexan without a proper drill will cause micro cracks that spread later. Note that Tap will bevel and/or melt edges to your specifications for a very nice look.

After breaking several windows during races, I switched to polycarbonate windows, which scratch more easily but are much much stronger.

When re-bedding windows, you want to have a good thickness of silicone. One trick I learned for this is to cut tiny squares of white electrical tape and placing them near (1/4" away from) the screw holes, so when you fasten the window in place there is still a thickness of silicone to make the seal. Don't tighten the screws until the silicone has set up somewhat, and then don't tighten them very much. Remember, you want a thickness of silicone to make the seal.

Masking over everywhere that silicone should not go (window, cabin top) is a good idea, as silicone that gets loose will both make a mess and make future painting / repair jobs go poorly.

I have an Express 37 with the original windows (very hazy but no leaks). They have very thick silicone layer (perhaps 1/8" thick). I'm not sure what trick they used, but it has been very effective over the years.

:: Where can I find how to repair Express Window water
:: leak?

:: I heard it is common for Express 27. Any article or
:: instruction for the repair?