I used what Toyota recommends for the Paseo which is 75W90, but I used Royal Purple synthetic. It definitely makes a difference when the engine is cold. Once warm, I don't think there is a ton of difference.
To make it easier on yourself, get a funnel and a tube to go on the end of the funnel. That way you can snake it down to the tranny fill hole. I have a pic in my build thread
here.