Always get a Carfax.
It's not even a question to ask. Since you are looking for a car to buy, get the multi-pack that Carfax offers. Carfax is a very good tool that helps in your decision making. It is far from flawless (they miss accidents, mileage discrepancies once in awhile) but very useful.
As far as this WS6 we need more info.
that the title is clear with no negative history, like accidents, excessive multiple owners, etc.. If the car needs nothing (has good tires, good exterior, good interior, etc) then $10,000 may
be a decent price for a 'private party' sale. If issues, even minor ones, then $10,000 may be too high. You haven't even stated if the car is an automatic or 6 speed. Everything affects price so details are needed for an informed 'guesstimate'
, starting with the Carfax.