Some sort of worm in the sand. I just saw something similar on r2r and they said they are harmless and actually help clean up left over food and what not. This is regurgitated info though.
Every once and a while I've seen a few group buys on them. I know there are a few vendors around here that sell them. I can't remember off the top of my head who the vendor was that put together the group buy. I also saw a used one not too long ago in the for sale section. That might still be around.
It's really the gut part of the clam that is most beneficial isn't it? I'd figure that's what holds the most good bacteria or natural probiotics in it.
To me that seems like a great list of equipment. My personal opinion is that light is probably a bit overkill for FOWLER but if you plan on moving to reef later down the road then it will be great.
Although it might be nice to get it cycling, if it were me, I'd wait till after the vacation beings the setup is so new to you. I would just be paranoid of having a spill or something. It would make the end of the vacation pretty crappy.