Congrats on a really low milage purchase. Plenty of info on the 919 around here. Starting with the basics, it's new to you and 16 years old. You should go thru all the fluids, look at the brake pads, chain condition, fork seals. Not a bad idea to do a go-thru on the forks, check the age of the tires using the DOT codes.
Give us a rundown on what mods you have, PCIII, shock, etc...
Pretty bullet proof bike really, not a lot of issues. Common things seem to be the FPR (Fuel Pressure Reg), Weak battery start issues have been reported. Some don't like the stock exhaust position, but California bikes don't seem to have the exhaust smell because of a cat. converter.
Many aren't too happy with the stock suspension, but the engine seems pretty amazing. I haven't had a lot of different bikes, but this one seems to be a pretty amazing bike.