It doesn't look all that bad. You might have done better with a pair of Adtran 612s though. Much better user interface, probably cheaper too. You could probably have used a couple of add/drop CSU/DSUs instead, depending on what you're doing with the three voice ports.
You (probably) don't want to enable FDL, which is like an "order wire" / kinda out-of-band management scheme. Doing so would kill IP management (on the WAN2(?) interface).
You mention that you want to peel off three channels: what kind of device is terminating the three channels? Are you going to feed some POTs phones directly with the FXS ports, or feed them as a DSX1 (fractional) to some flavor of PBX / Key System?
The channel map appears to be pretty straight-forward ... just make sure you peel the same three channels on each side. It says four channels per hex digit ... a hex digit is four bits (counts from 0 to 15 ("f")).
I bet you'll be an old pro with these things after a couple hours.....
Good Luck
Scott