If you're also breaking in a rebuilt motor you're in luck. Just drive it like you would breaking in a motor; vary the speed and load, run through the gears, don't hurry the shifts. Change at 3-500 miles, refill and Bobs your uncle.
Be careful with what lube you run because of the yellow metal synchros. I've done a pant-load of research and found Swepco 202 is apparently the beans for our type of transaxle. For the break in I wouldn't worry too much, but after that go as good as you can afford for longevity. Here are a couple links for fun reading.