2007 Outback 3.0L auto box not going into Reverse / Park

[Andrew Dodd]

 Any ideas welcomed- 119,000 miles  VGC  and well  maintained vehicle  but  auto selelctor has begun to stick  and unable to selelct R/P  from DN - seems to happen on an  incline- mmaged to move it when on the flat and lifting the gear selector slighly. Full fluid levels  but appearing in need of fluid change as not red any more - might this sort or is she a gonner ?