Got my headlights in the oven right now...
When i reseal with silicone, what exactly do i do?
Just put some where the old silicone was and hold it together with clamps?

 

You should probably strip off the entire seal and add a fresh one. Mixing old with new is only looking for problems in the not so distant future.

I honestly do not like clamps because they can put uneven pressure on the housing. Last time i did that, I used a pair of strap tightners, the same ones you would use to secure cargo in a pickup or on a rooftop.



Like this the belt will put even pressure across the entire headlight and make sure the seal dries evenly.

As for the actual sealant, if you want to do a professional job that will last another decade, Nissan Butyl Rubber is the way to go. You can find some on ebay for about 20-25$ shipped. It's not a silicone, so you don't need any finesse you would need with a liquid substance and it dries harder than silicone and it's much easier to contain as it wont disperse when you put the straps on to hold the headlight nice and tight.

I was a first timer when I had to reseal my headlights and watched a few vids on youtube, the result was way better than I expected.

 

double post..