is the dark grey ring around the bulb nesesary?
would my lights shine in the wrong direction, or be brighter without it?



whats the best way to glue it back together? dig out all the old glue and get new stuff or just heat it with a heat gun and push it back together?

if you remove that then they will be much brighter and probably blind a lot of people

IMO you should use some clear silicone glue. Heat up the old stuff (it's easier then removing it) and add some silicone glue and put the glass back on.