Yeah, he did kill the trans. At this point, without the oil in there, he's basicly, more or less, welding parts together in that thing. He can try adding oil at this point, on the premis that when it cools down it might loosen up somewhat. Even if he didn't destroy it completely, it's going to be damaged, and now it's just a matter of time. It's very,very hard to get parts, or even replacement transaxles for these things.
By the way, how many miles on this thing?
The place where you put the "mercon 3" ATF into it is: where the speedometer cable goes in. There is a small 10mm bolt holding the speedometer cable down to the trans. This cable would be going straight down into the trans, nearest where the steering shaft comes out of the drivers compartment. Once the 10mm bolt is removed, you have to grip the metal part of the cable housing with pliers nearest the trans, twist it back and forth a little to loosen it, as you try to pull it up and out. Once it's out, there will be a little gear on the end of about a 3 inch stalk, be carefull not to damage it. There's a mark on this stalk , but really, just fill the trans up to about an inch from the bottom of this hole. You will need: a long skinny funnel sometimes refered to as a tranmission funnel, and "mercon" style automatic transmission fluid (atf) Yes, I know it's a manual transaxle, but this it what these, and many other manual transaxles use these days, this fact is unbeknown to many people, including auto store counter help, and even certain mechanics! The total capacity of this trans is about 2.5 quarts. Good luck, and do keep us posted.