Hi! And welcome to the forum! You couldn't have picked a better place! Lots of 919 owners here too so pull up a chair.
Here's a pretty decent checklist of stuff to look for on a new bike: http://www.motorcycleinfo.calsci.com...e.html#NewBike
The big things I would check out are battery (in fact, after sitting that long, I would insist on a new one), tires, cables, gas, lights, brakes.
First service is at 600 miles and it's mostly to check brakes and that all fittings are still tight. The owner's manual is a worthwhile investment. They can be had on eBay for about $30. There are electronic versions available too - PM me if you want a link.
Break in period - a couple different trains of thought on this - ride it hard, fast OR take it easy for the first thousand miles or so. Here's a good page on break-in philosophies courtesy of our own Lord Duckhunter: http://www.919.org/breakin.htm
Price - it's a new/old bike and it's not likely they have people lined up for it. And the season is past the half way point in your area. They're not going to take a loss on it, but should be motivated to sell it. I'd start at $5700 and expect they would meet me somewhere around the 6K mark. Don't let them barter with the extended warranty -- on established bikes like this one, they are generally not worth it. However, if you need gear, maybe they will toss some stuff at you for cost.
Good luck with the buy and welcome aboard!!