My V8 Soarer had the dreaded moisture in the headlights, and one was also a bit hazy while the other has some dirt etc sitting on the bottom, so I figured it was time I got brave and had a go at the removal/cleaning process mentioned in various places. Removing the headlights would also allow me to have a look at making a BFI.
After getting the light out and split, I am not convinced that the front glass seal is where the water is getting in. The light assembly fits together like a clam shell, with the front lens slotting into the back shell. The tongue on the lens slides in about a centimetre into the slot and the entire joint is very well bogged with a silicone type sealant. So not only is there a very large amount of sealing, but the sealant doesn't dry out and crack, but remains workable and gets quite soft when hot e.g.. out in the Australian sun, which would keep the sealant pliable and well, sealing I guess.
Apart from the lens, the shell isn't a sealed unit, there being 2 drain holes with short tubes on them which appear to provide ventilation to allow the moisture to dry out as they are not at the bottom of the unit as a drain hole would be.
Unless you wish to physically clean the inside of the lamp, I don't recommend this procedure unless you are certain this is where the leak is.
After doing both headlights, I still had water leaks when I washed the car. I waited a week for the mastic to settle, removed both assemblies, dried them with a hair dryer blowing through the bulb sockets on a cool setting, then ran another bead of Mastic around the seal joint. I have since washed the car twice, and no more moisture! So if you only have condensation and the lights aren't dirty on the inside, try just running a fresh bead of sealant around the joint.