Simple question and not wishing to offend. Are you competent enough to judge the condition of the machine and its components..? If the answer is no or not sure then for what you are planning to spend it would be well worth your while contracting the services of a competent professional service technician to inspect and provide a service report (TA-1 & TA-2 in Cat terminology) for the machine in question. So what if it costs you $500, that's less than 1% of the asking price and would be money very well spent IMHO.
Other thoughts. Does it have any service/maintenance history and can you get to see it..? It may look to be in good shape but does it look from the outside at least like someone's taken care of it, for example are all the linkage pins oozing grease and are all oil levels in the correct range..? Do all the oils (except the motor of course) look clear and bright..? Is there any trash in the belly guards..? Things like that can be good indicators of how well a machine has been cared for in its previous life.
I don't see why the hours would be a concern if you go into the purchase with your eyes open. However I would think about planning to spend money on overhauling major/minor components in maybe the 10-12,000 hour range. So long as you budget for that everything should be fine. All the components on a 938 should be capable of being rebuilt at least once.