If you look under the front skid, the plug should be obvious.
AggiePhil - I remember seeing someone post about accidentally draining the ATF instead of Engine Oil, then overfilling the engine oil and starting (i.e. drained ATF and overfilled engine oil = bad news)... so my advice to you is to make sure you know where both Transmission pan and Engine Oil Pan are so there's no room for confusion. Check out the FSM for diagrams or find a thread with pics to bolster your confidence.