As it's virtually due a service, use that as a bargaining chip. Get them to throw a service in. And change the belts as well. And check the rockers for wear. Not saying you'd get all that for free, but they're all things that you need to be doing when you buy a second-hand Duke, and someone's got to pay for it.
Right now I'm changing the oil in my 748, and it's done 41000 miles in 3 years.
You can't do better than read the exhaustive buyers guide here (see Shazaam!'s post)
http://ducatisportingclub.com/xmb/vi...d.php?tid=9331