Bin it and get another, if you manage to get it apart, fix it, put it back together again and it be waterproof again i'll eat my proverbial hat.
i know this is an old thread but i've done this with my headlights on my old car. what u need to do is put the lights one at a time in the oven for about 30 seconds the glue will melt first if u leave them to long it will melt the brackets it saves so much time and does a neater job, afterwards get a product called tiger seal its black and wont budge at all job done in about 2 minutes!!!!