LOL Asking if they are loud is an understatement. I am proud to be an owner of guinea hens and wish I had more. Need a female to increase the flock. Yes, they are noisy but it serves a purpose and if you don't mind noise I would go for it. There should be a lot of stories headed your way about personal experiences with guineas from the crew here.
Guineas are the best early warning system for a flock of chickens, geese and even ducks when it comes down to a predator lurking around. The guineas don't skip a beat when there is something going on near the flocks.This also goes for people who visit your home, guineas will let you know, cars coming up the driveway if they are free range, the guineas start trumpeting.
I have had guineas swoop down and scare off fox, cats, dogs...pretty much anything that does not belong in the yard. My guineas help me out with a bald eagle who tends to use my free range birds as a feed source. If the eagle gets low enough and the guineas see it they trumpet out as well. The flock gets used to the guineas and always heads up for the chickens when the guineas react. I definitely consider them a bonus plus the fact that they are excellent bug eaters. Guineas would rather forage for bugs than eat from the feed dishes. Yes, they do need feed though.
You should get a lot of positive reaction from this forum regarding your questions... Good luck and good reading... Steve