Toyota Fortuner, Transmission Upgrade Possible?

“I am posting this here for kumar.”

Dear sir,
I am using Toyota fortuner AWD which has 3.0 litre diesel engine with 5 speed gear automatic transmission. I want to upgrade my transmission to 8 speed automatic transmission. Is it really possible to change the gear box.? I am ready to spend money. but is it possible to change old one with ZF 8 gear automatic transmission? Will it work properly if we change.or any complications may occur? please do give your valuable suggestions. if we upgrade what else we should upgrade along with that transmission box. i really like the jaguar xj round gear shifter – anybody please reply. If i am technically wrong please let me know.