I'm no expert, but I did practice brisket a lot last winter getting ready for a new bbq comp season and I think you'll find that it's not too scary once you get into it. It's a big peice of meat and doesn't need to be tended a whole lot. Using a mop with the flavors you like similar to the one that bigwheel suggests is a good way to get some additional flavor while adding some moisture. If you don't have time to come up with a mop, then apple juice works just fine. Spray or mop anytime you have the smoker open is a good rule of thumb.
For sixteen people you'd want to do about 13-14lbs raw. Can be done with either a full packer or two flats. Flats will cook up faster, so if you don't have a lot of time to invest then they might be the way to go. If you've got a bit more time the packer is fun too and gives you the opportunity to do burnt ends!
All briskets have a mind of their own and they are not done until you can stick a probe in them like a knife going thru butter. This can happen between 185 and 210 degrees internal temp usually.
Sorry to be so long winded, but when I get started I just can't stop sometimes.
Have fun and remember that even if you think you messed up, someone will tell you how wonderful it is