Not a stupid question. A fail safe is easy to hook up. It plugs inline with the throttle servo. Just plug the throttle servo into the fail safe and the fail safe into your reciever. No battery needed, it runs off the recievers power. The fail safe will kill your throttle if the reciever doesn't get a signal from your transmitter or if your reciever battery gets to low. There is a dial on the fail safe to set where you want throttle to go if it sences trouble.
You should beable to get one at your local hobbie store, Tower Hobbies, E-Bay, etc. I lost a nice boat on it's first run because the reciever got wet and it ran in to the rocks. By the time I got to the boat the engine over heated and was ruined.
The only thing it won't protect against is if your batterys get unpluged so make sure they can't bounce loose.