1985 944 Stripped Transaxle Fill Plug

Vehicle Information: Model(924/944): 944; Year: 1984; Engine (type, size, modifications): 4cyl, 2.5L, stock; Total Mileage: 131,800;

How can I remove a frozen (and stripped!) fill plug on my transmission? The problem is that I have already drained the oil out.... Or, is there any other way to get the transmission fluid in besides using the fill plug? I have a spare transmission, and was searching for other access areas that would allow me to get the fluid into the transmission.