Another option with Yamaha's digital mixers is to use an aux output feeding a control room, put a computer in the control room, load up yamaha's control software, and voila, an instant test mixer on your computer. It isn't quite as nice as the real thing, but for training/confidence building, it can work. It would also save the expense of the ADAT card and a recorder.
You could also go the other direction, have a
very experienced operator on the computer sitting next to the console, and the trainee can run the console....any mistakes could be quickly overridden by the other operator, minimizing the trauma on the congregation. This way, you can hopefully get the best of both worlds.
I believe, in answer to Tom's concern, that it is possible to route the pre-mute signal to the recorder, which would allow your scenario to have [some of] the effects of not muting a mic. (it won't decrease gain before feedback, but IMHO that is the least of the associated problems; you really won't have feedback on the recording anyway (hopefully!
) )
mike