Epoxy? No...you don't want to use epoxy. If anything, use more silicone to reseal them.

If you do it right...you don't need any extra silicone.

I've done mine and a few for friends, and I think the easiest thing to do is to heat the whole assembly in the oven for a bit to warm and soften the glue...then as you pull the two peices apart...have a friend cut the glue apart with knife...(kinda like cheese stretching on a pizza slice). Then once you have them apart, do your business, then put the two pieces back togher, and put them back into the oven to reheat and soften the glue. This way you'll get a good seal and be able to close them back up nicely. If at the end, you want to add some silicone arount the edges, go for it.

As far as taking off the bumber, you'll see the clips/screws/bolts as you go. Pretty self explanitory.