Wow NICE pickup, but a bit on the delicate side and also a rare lizard, too rare to just keep as pet, hope you want to breed some day, all bloodlines needed. If he was mine I would stay away from aspen but not the worse stuff out there either. Just for the time being I would sugest keeping simple. Tile would be a good substrate just for the moment. In the long turn you want a dirt based substrate mix heavy on play sand. I would say your terrarium is a bit on the small side specially considering the need for a good termal gradient. You should also include a cave for him. Feed allot of dark leaf vegetables and ocasional insects.
Hope you know some good Uro husbandry, I would go for mali uros anytime before trying these.