If you had searched the 
Guinea Fowl forum, you would have found more information on guineas than you would want.
Guineas can be loud, obnoxious, weird and many people make the claim that they are awesome guard dogs.  Guineas are not good guards and in many cases cannot even protect themselves from predators.  In large groups, a whole flock of guineas have been known to go after daytime predators en masse.  Sometimes this works as a deterrent but in more cases than not, it exposes the guineas to the predators who will pick the guineas off one at a time until there are none left to return for.
At night time, unless in a secure coop, guineas are very susceptible to predators because of their poor night time vision and the fact that they sleep at night.
Guineas will become extremely noisy when sounding an alarm, however there is no guarantee that the alarm will be a valid alarm.  They may go off simply because you are wearing different colored clothing than you normally wear or you approach from a different than normal direction.  They can alarm at any imagined threat to the extent that their constant alarms get ignored and when a real threat occurs it gets ignored.
If you think you can get a couple of guineas and expect them to chase off your mink, it isn't going to happen.  To do any good you have to have a large flock of guineas and even then they are more likely to become predator food than they are to chase off your mink.
If you want a long-term solution to your mink problem, learn to trap them and do so on a constant basis rather than once you just happen to see them.