It's a great road to travel. One of my favourites. It is used by trucks so your rig will fir it OK. It's a full 2 lanes each way. I get my rig down the hill to Harrietville in low gear without touching the brakes much. Any rig that is not overloaded will get you over easily even if a little on the slow side in places because of the bends in the road. I suggest you don't let the timid ones put you off with their "horror stories." It's not as bad as as they paint, they are just not confident drivers. There is no need to be like them, most of us enjoy the trip.

Do some armchair driving of the route. Most of the Youtube videos were taken in wet weather or in snow (when you are not supposed to take a van over that road.)

Amarok on the Great Alpine Road (Harrietville to Hotham and Dinner Plains)

Driving from Dinner Plain to Harrietville (highlights)

Driving from Dinner Plain to Harrietville (full version)  This one takes 49 minutes to watch.

Have some fun with these -  Driving the Great Alpine Rd - general index.