The volunteers can rotate off or come and go as they please. The more participation, the better the buy-in. The mission of the implementation team is to balance the requirements and desires of the staff with the capabilities and limitations of the technology. On the training issue, you must deal with how to set up your training, your goals and your timetable. Some papers choose to hire outside trainers for the staff, but everyone agrees that in the end it pays to have as many people as possible in the newsroom trained as troubleshooters.
Many papers dedicate one person to oversee training in newsroom.
It's important that you spread expertise around the newsroom. Don't suffer the trap-door effect of losing your one and only master trainer to the Microsoft Network at double the pay. You need to work closely with your paper's technical support people. Often that means having a staff liaison who can translate technical jargon to the staff. And it means having the technical support people readily available on all shifts.