@tsarstepan,
My first race was the Corporate Challenge here, in '09. It was a large race (and I bet yours will be, too), so be aware that you'll be handling other people in addition to your own time. I don't mean a big thing, more like not stepping on them, or going around them. Just like with cars, head to the right if you are slower than the group.
A June race can be
very warm. I own a fuel belt and I love it (and I don't care how dorky it may look). RP just holds a bottle, or uses a hand canteen. Dress as if you were dressing for weather that was 20 degrees F warmer than the real outside temperature.
For me, it took a little over an hour but I mainly walked rather than jogged, but was very, very pleased that I didn't have to stop, as I saw others did. Came out of it hooked on racing.
Have fun!!