Dan,
The pink helmets are just something the Philly region uses, I don't know if others do. We have fun with people wearing them.
You do not need to be a member of the SCCA to run in Solo II events, it will just cost an extra $5.
Insurance will likely not cover you at a Solo II event, but there is very little to fear. For the most part, the worst that happens is that you spin out and hit those little orange cones. They don't hurt anything.
Autox/Solo II has a lot to do with tires and suspension. Any race compound tire will blow away the best street tire. But most people, including me, recommend to run your first year on street tires. This will help teach you car control and how to drive the car well, so that when you switch to race tires, you'll be able to fly. Horsepower may or may not be important, depending on the course layout. I tight course may hurt a high hp car, as it is hard to get the power to the ground well. A more wide open course favors cars like us. Weight has a lot to do with autox. The heavier car will have a hard time going right/left/right quickly. So we have a big advantage here.
The lenght of the course depends on the set up and the size of the place you are running. In my region, the shortest course will be about 30 seconds, the longest will be closer to 50 seconds.
Do some autox, as I think it's one of the best ways to learn how to handle and push your car. But you've also got to try the open track events. They are on an entirely different level.
Steve