Viscosity is not crucial on a 1997: 5W30?, 10W30?, 10W40? Its not going to make much of a difference. If you're burning or leaking oil, go with the thicker grades
Filter: Subaru OEM?, or Fram?, or Wix? etc. IMHO it really won't matter.
WHAT IS IMPORTANT is to change the oil and filter frequently, more frequently than recommended. Keep that oil clean!