I have four 850s. The shift lock does not work properly on the two with autos, a minor inconvenience. The smoke from the dipstick could be a clogged PVC, relatively easy fix if you are handy with tools. All of mine have needed it. The oil leak if it is on the drivers side could be the rear main bearing seal(expensive fix}. However one of mine had a fairly significant leak from the rear main that was dramatically improved by replacing the PVC which was partially clogged. I agree with the others that that is a great price if you have it checked out by a volvo mechanic and no other problems are found. A compression test before purchase would also be highly recommended. If it checks out you could have a great car to drive for a long time to come.