I have a 98 S70 T5 with a manual transmission and 48K. You want to have the
air conditioning checked (make sure it is blowing very cold air) since the
air conditioning fail often. I suppose transmission fluid should have been
changed but you can always do that. There are a couple of recalls but
any dealer can run the VIN and tell you if they were done.

I would check the records for re-occuring problems. A re-occuring problem
should be looked at closelt. It is not uncommon to see many small problems; but, once fixed they should not return.

70K is timing belt replacement. The 98 70 series use the same service
schedule as the 850s (99 and higher have different service schedule).
Same filters, etc. So, many of the things you have learned from your
850 apply. Also, note that 98s were sold as early as April of 97 so
the car may be older then you think (build date is on the driver door).
Around 60K I bet it will need tires and probably brakes and front rotors.