Can I drive my mortorhome to Tibet?

I'm doing the Silk Road in Motorhome, start the route from Venice Italy in June and reach the Almaty in masseur in mid-October where I have my Motorhome parked in customs until next year in May-June I want to restart the route through China and Nepal, could you help me with all the procedures and requirements of the Chinese government and Nepal? I intend to follow the Wai to Southeast Asia or India. The
travel agency named Great Tibet Tour says I can't drive my motorhome to Tibet.

Anyone knows more?