Hi, not that simple IF YOU DON'T ALREADY KNOW WHAT TO DO. The number one thing you generally want to do is to get a lot of agitation in the vicinity of the "cathode" (that's the part where the silver plates on to). This largely determines how much plating current you can run. (If you run too much current then you will get reactions that you don't want, mainly "sulfiding" where the cathode will get dark and you won't be very successful getting silver out.)
This differs from normal silverplating in that the silver ions are not hugely available - only a small proportion are at any moment, and if you try to take more than are in the immediate vicinity of the cathode, other reactions happen instead.
The typical method for mini-lab machines used to be a rotating cylindrical cathode. So you would have to find some compatible "brushes" and "slip rings" to transfer current to the cathode, as well as find a way to make it removable.
Your best bet is probably to look for an old minilab unit (with rotating cathode, and manually adjustable current up to about 15 or 20 amps). Then have someone in your darkroom learn how to operate it, mainly learning how to estimate the silver content of the fixer, and from that estimate the max plating current and how long to run. Then, when a batch is nearly finished, recheck. That person should probably dictate to the members how far to use the fixer (preferably multistage) in order to get consistent desilvering. If your group is not willing to do this, then you probably don't want to take it on.
If you run small enough volumes that you don't need a machine like this, there is another type that runs such a low current that it doesn't need agitation. There's a guy on this site who is a dealer - (see the "Silver Magnet" ad on the bottom of the page). If you want to do minimal work, and IF your quantity of silver is low enough, this is probably a very good option.
I should have said at the beginning that you need to have an idea how much silver you have in order to make a reasonable decision. Also, you may have regulatory issues with the effluent that are already being handled by your service company. So, just some things to look into.
If it makes you feel any better, the outfit handling your cartridges probably isn't making much off of it. It's so impure that refining costs are high, the silver loading is somewhat unpredictable, and they probably take an occasional beating on a cartridge. If you take away their income on the silver, then the problems will likely become yours. In fact, the first thing you should do is probably to sit down with the account rep for your service provider and discuss these things with them. They may be willing to let your members take over some of the maintenance in exchange for a better return.
Best of luck.
Ps, I should point out that I'm mainly speaking of fixer, only. If you're using bleach-fix, the electroplating is much more difficult.
