The fact that you used an allen for the drain plug tells me it was definitely the transmission fluid (red in color or darker depending on its condition).
On the 5eat Automatic:
Oil Plug: External Hex
Tranny Plug: Internal Hex
Differential Plug: Torx
As long as you havent run the engine you should be fine. And yes, they actually drain it properly in step 4, but show the wrong plug initially.
And no, you only need to fill the dipstick on the driver's side of the car. The other side is the to fill the differential and would only need filled it you drained that as well.
The dipsticks for the diff and trans are actually labelled accordingly. They should say "Diff" and "Trans" or something like that on them.
Last edited by Mill; 11-19-2012 at 04:05 AM..