Lots of such qualifying details are not uttered, because they are assumed according to certain maxims which govern constructive conversation among rational people.
Where can I find these maxims written down?
The Hippocratic Oath is probably a good starting point, given that the guy asking for the money is a surgeon.
This procedure has been done on monkeys in the 70's. It might not give this man any control over his new body, but at least he won't suffocate to death from spinal muscular atrophy.
That is implied, otherwise first 'head transplant' would be done centuries ago by some dr Frankenstein.