Heh...first off, Leos have a very sweet temporment...I have never seen one to bite, and most will sit happily on you lap for warmth and will take bugs from your hand. However, the babies are flighty and high strung...as adults though they are mellow and personable...the only lizard I think is more freindly is a bearded dragon. (gets yelled at by all the leo fans)
A twenty gallon is a great size for a leo...it can hold more than one too, as long as they don't fight. Just be sure to give the tank plenty of hiding spaces...Leos love their hidey-holes. Make sure you arrange the UTH and lamp so the leo can regulate their prefurred temp.
The zoomed diet works, but...if you even want to use it, you have to teach your gecko that it's food using many hours of jiggling it with you hands and the like. In between then, the gecko will need to eat bugs...leos are predators, and they do like to hunt. A normal leo will walk right over prepared food and not understand that it's edible...they need to see wriggling.
I hope this helps, and I hope you like your leo. ^^