check online for tranny rebuild kits,for your make- model.
if its an auto...pull it,take tranny to carwash..shoot it down w/engine degreaser-hard brush/elbow grease-get it as clean as any firearm you have ever held!!!.take home-dry it.(blow dry w/ air comp.).start at front of tranny(bell housing/main pump)-stack all parts the way they come out.parts go back same way they came out...last first-first last
when reassembling-make sure everything is very clean!!!