You’re right. That’s an outdated uni, but for the price you did pretty well. It should work fine for learning. 24" is a good general-purpose size. After you learn and ride around for a while, you’ll know if you want a better one. There are definitely other riders in the Bay area. Maybe at that point you could get in contact with them. I’m sure they’d let you try out some of their gear.
The uni only goes forward and backward, so that’s all you have to work with to keep your balance. If you’re falling to the side, you have to turn in that direction and then use the pedals correct your balance. It sounds hard, but your muscles will figure it out on their own as you practice. It becomes second nature.
I did the 100 reps thing at the beginning, and I think it helped me get comfortable with the way the unicycle moves. It’s not necessary though. Most people I know started out going back and forth on a fence and then went straight to the let-go-and-pedal-like-crazy phase.
Idling is much harder than riding. You should definitely try to ride first. After that, you’ll want to learn to free mount (i.e. get on and ride without support). After that… whatever. Some people learn to hop. Some people learn to idle. One weirdo on the forums last year went straight to wheel walking.
Whatever you do, keep reading and posting. The forums are great for motivation.
You might have it all figured out by Monday. The rumor is that it takes about 15 hours on average to learn to ride.
Sitting without squishing yourself is a common topic. If you do a search you’ll find lots of advice. Here’s a nice thread complete with an awesome scientific drawing to illustrate the point: