The Proposal involves the following circumstances:

Purchase of return transport to the International Space Station from Russia ( who of course have already sent tourists to the ISS).

Purchase of one of the Shuttles from the US on the basis that it is bought as tethered in place on the ISS. In space the Shuttle will have a much less requirement on servicing and should be operable for a period of at least 5 years - note that for every launch from Earth approximately 6 - 9 months of intensive preparation is required - this is the weakness of the Shuttle the stress of take off and landing, once in space this is a spaceship of supreme elegance and durability.

Purchase of permanent docking arrangements from the International Space Station.

Purchase of transport of fuel and maintenance for the Shuttle to the ISS from Russia.

The flight from the Space station should room for a least 4 passengers - a more ambitious project would convert the cargo bays to extra passenger space and fuel storage. It will orbit the Moon in a law a protectory as safely possible for 3 Earth days and then return to the space station.

For the increased number of passengers then other countries such as China will soon have the capability to send people to the ISS.

This is broadly a process of make-do something that is perhaps beyond the American psyche- historically it has never been a requirement . Given the right anount of money the US will sell one or two of the Shuttles ( one goes to the Smithsonian Museum) .