All the info you have is correct, its all possible, but BEWARE: South African Customs are there for the sole purpose of testing your patience. Dont expect a reply to any emails!
An Australian named Stephan (firstname.lastname@example.org i think) did sell his bike here legally about 3 years back (as have many others), he will have all the info you need. If cant find him contact me and Ill find out more for you.
"If we don't find something good at least we will find something new." Voltaire