Need advice about auto transmissions?

this morning things were perfect. on the way home i noticed it was moaning and struggling to get into 3rd or 4th (which ever....the lowest gear). i thought it might be low on auto fluid so i pulled up to get some. then when i tried to reverse out..... NO REVERSE. its a 98 holden commadore. can any please give me an idea what the cause maybe so i have a fair idea how much money i'm in for. THANX......