Leaking tail lights

This is my first post and want to say this is a great forum. I have been the proud owner of a 1990 300SE for a week now and am bowled over at what a great car it is when compared to a 116 or 123!!

I have water in both sides of the trunk and found the tail lights to be the culprits. I suspect it is the tail light seals. Is it good enough to use some body sealant or should I replace the seals? also how tight should the nuts be?

I will also replace the trunk seal as a precaution. There is only a small amount of surface rust, which I have treated with a converter.

Thanks. All help appreciated.
Greg de Klerk