^Looks like that center rail will be doing the work of the guide wheels/upstop wheels as you stated. The main rails will be the load bearing rail where the road wheels will run on.
Viper is an antique and is not causing any headaches for the park per-Se. The riders yes, but not the park...
Viper is one of my favorite coasters and is a people eater.
It all depends on the country of origin for the parts. If the track and ride components have to be shipped half way around the world then yes it would be more expensive than say S&S installing something at Lagoon Park seeing as they are both in Utah.
Doesn't really matter at this point because even if they do announce something "Major" it won't be open until December at the earliest and that's being EXTREMELY optimistic.
Roto-Shakes are maintenance nightmares thus why Knott's (and every other park for that matter) removed theirs. They are a little uncomfortable to ride in my opinion.