I don't know about 2 & 3 but you need to talk to whoever you got your financing about #1. Some companies will apply any extra paid towards the principal. Others will just credit the extra towards the next payment. You might have to specifically note that you want the extra to go towards the principal and not the next payment. I'd check after a month or two to make sure it was being applied properly too.
I worked with a guy that had financing through Chrysler and he had been sending in extra each month for a while. He called to get a payoff amount and found that the extra hadn't been put towards the principal only. Instead he it was just 5 months before his next payment would be do.