To go from 280 to 312 will need calipers carriers discs pads hoses needed for the front as calipers have a different connection. Also you will need 6mm off spacers for the carriers
Track days are not races so you go at your own pace. I start off slowly and build up through out the day, I only have the one car also and my suspension is standard.....tho rest of the car isnt lol
It's worlds apart from my 3GS. I turned them both on the same time and the 5 was up and running and doing stuff before the 3GS had started. The maps does look shit in satalite view but I always use nap view anyway