As far as amount of transaxle fluid to add after a drain, would it be fair to measure the amount drained and replace with same amount?
It is but the fill requirement is ~3.7 quarts. Buy 4 quarts, ensure the car is level, and add until it comes out of the fill bolt.
not only this but you can't accurately account for the amount left in the container as you never really get it all out, could be some small spillage, or other factors. Just fill it till it comes out of the fill bolt like others said
Check the dealership parts department too. If their fluid price is close: they will also have the fill and drain bolt washers. If you want to go kosher they should be replaced. Be prepared to pay $2~3 apiece for them. Torque for both bolts is 29 ft/lb. They're identical, 10mm hexagonal pocket cap-screw style. You can get 3/8" drive "sockets" with the required allen key shape. Stanley makes a set, for one.
Good find! I was looking for WS 2 weeks ago and didn't know WMT sold it online. I found it on Amazon, but it was about the same price as local dealer, $9/qt.