The board is available but still in a limited quantity. I will have a new batch of boards made that will make it more widely available and I will add a buy button to the site then.
And you're right that all the SMD components are already assembled. So the board is functional as is and you simply add the through hole components for the functions you want to have.
The inside case dimensions are 120mmX100mm and you can see more information here: http://www.hammondmfg.com/1455.htm
. The one sold with the board is the 1455L1201 and the 1455N1201 is also available for those who will want the SLC OEM carrier board. So you can use a case that has those dimensions but if you want more than just the base board, you have to be careful about the distance between slots due to the connection between the boards. There is some margin and you can use different components but this would have to be planned for.