Yes, change the hydro's fluid and filter. Even if the previous owner change it, it will offer you some peace of mind. I have an X530 and have been very happy with it.
Found a nice X500 for $2400...290 hours and in excellent condition. Probably gonna pick it up Thursday.
Any quirks about these I should know?
Should the trans fluid be changed, because I'm sure the owner hasn't done it if it is changeable.