A 10W30 should be fine, depending on your climate. 10W30 should be fine between around -18*C and +38*C. Don't worry about leakage, I gaurantee you will not have a problem. I hear this so much it's strange, but I have never encountered this, nor have I met someone who has had this problem...it always seems to be a friend of a friend who had that problem. Read the last FAQ on this page:
http://www.mobil1.com/USA-English/Mo...ics/Myths.aspx
I don't know off hand what weight oil to use in the transmission, so just ask the people at the place you buy the oil from. Better yet, phone the service department of a Toyota dealership.