1) Certainly you can do it on a hybrid. Obviously make sure whatever bike you choose is in good working order and fits you well (you might find some interesting new pains around mile 75-80, but you certainly don't want ones you know are there nagging you from mile 25!)

2) I would guess 3 months is adequate. I never really trained for (and didn't even plan to ride) my first century. There is quite a difference in a metric vs. a mile century. I ride a metric almost every weekend now (after a few months of consistent riding) and think nothing of it (sometimes I ride two!). Going 100miles is still a mind over matter (muscles) experience for me though, but I can do it if I put my mind to it.

Still, I think you have time to achieve either if you get a good training schedule going.

3) No help there; I just ride

I think one of the most important things is going to be planning the ride out. Is this a supported century you are aiming to ride in or unsupported (on your own). If it's supported you'll likely have rest stops and water refills planned out for you. If you are doing it on your own you should think about things like that as well as what route you want to take (doing a climbing intensive century would be no fun, if not near impossible, if you don't normally climb on your rides). Planning a route with safe places to pull off to the side and stretch/eat, especially in the latter half, as well as places you can stop and restock your water/food is probably wise.

For reference last weekend I went through 4 water bottles with one being a sports drink (so that's at least 1 refill stop, I stopped twice) and 3 1/2 powerbars. After mile 75 or so I stopped to stretch every 10-15 miles for a few minutes. You may not have to stop just to stretch; I was hitting some hills and the mental game was getting harder

Good luck, and have fun