03 explorer trans hard shift neut/drive

Well guess what another trans question....03 explorer just over 70,000 miles. Trans just starting to shift hard going from reverse and nuetral into first gear. Trans slips when going into gear, press gas pedal, engine revs....then the trans catches and slams into gear. It does not happen all the time. Just came back from the dealer with all the fluids changed at 65,000 miles. I this the begining of the end? How can I check fluid level or add additives? Seems to done underneath the car? Thanks for suggestions.