The red board is NOT for the USB model; it's for the arcade models. (If you get the red boards, you'll need an optipac or optiwiz interface, also.) However, happs does have a "version 2" of the USB boards which are (I heard) an improvement of the old USB boards.
So if you get version 2 of the USB boards (which are not red), it's just swapping the two boards and plugging in the USB wire. If you go the red board way, you'll need to swap the boards, connect them to the optipac/optiwiz, and connect the opti--- to the computer. Both are easy.
Divemaster has both type boards (AFAIK), and they're cheaper than direct from happs.
Disclaimer: I have the arcade red boards and the older arcade happs green boards. I do not have either version of happs USB boards. I like both versions of the arcade boards on my optipac. So I'd encourage you go the red borads + optixxx way, if you don't mind the additional cost of the optixxx.