I also have an umbrella liability which covers when my auto or homeowners liability leaves off. It's really worth having. Check with your insurance agent.

Re a release of liability--I was told in my business law course (that was back in 1980, though) that they're not worth the paper they are written on. The injured party can always claim negligence which pretty much invalidates the release.

There are Good Samaritan laws in almost every state that are supposed to protect persons assisting the injured. Check yours. However, in Oregon, at least, thanks to a state Supreme Court case a year ago, you could still be ruled liable in case of negligence or trying to perform a task beyond your ability. In this particular case, it was untrained persons trying to get someone with a broken neck out of a car wreck without stabilizing the spine first. In other words, if you don't have the training, don't try it. Carry your first-aid certificate with you.