I owned a 320is for about ten years and purchased it with 39k miles on it. If a car is only driven short distances the oil should be changed about twice as often under normal driving conditions. Can you find out more info from the owner as to the distances driven on a daily basis? If if was maintained at a local dealership their computer should have some info available.
Mechanically you can have a compression check done to determine if there has been premature wear on the motor by comparing the current compression readings to the new specs.
2004 E60 530is, Delivered 12/12/03, TiSilver/LGrey, PP, SP,PS, PDC, ACC, FRS, Step, Xenons, clear bra, body colored rear inserts. (Retired, 1983 henna red 320is)
2004 Corvette Z06 Commemorative Edition