First off, how often should I deep clean my tank (it's a ten gallon)? And how do I go about doing this? Do I need to change the sand completely or can I just wash the stuff that is in there? What about cleaning the inside of the tank? Is hot water fine then rinse it with dechlorinated water? I'm coming up to one month with my tank, and just wondering when I should do this. I scoop the sand to take out the stale food they like to hide as well as the crabbie's poop

My second question (I know it's more like my tenth, but second topic), how do I sex my crabs? I know what to look for, I just don't know how to get my crabs to show me their undersides. Any tips?
I think this is all I need to know. My boyfriend and I seem to be getting into a routine with the daily cleaning. We're planning on adding a second level. Oh, that reminds me, I have read that people add moss to the tank. Where would I go about getting moss? What type should it be? How do I disinfect it without killing it?
Also, I had driftwood in the tank, but it got moldy. Is this normal? Can I just clean it off, and add it again? Is there a way of preventing mold?
I'm so full of questions because I want to make the best environment for my hermies that I can. Slowly, but surely it is starting to come together. Limited funds aren't helping either. Anyway, I think that's it for now. ANy, and all advice is appreciated.
Thanks
Fiver