Hybrid

You are Dr. Agon, a recognised brain surgeon, retired lobotomist and leisure time craniologist, and he is one of the best in his field. People with Aneurysms in the brain trust him blind. But since a few years people have to consult someone else for problems with the brain, the rather unknown company Dr. Agon is working for now pays more than any hospital in the world could afford to keep him employed in the white field of medicine. And the company's interests are way closer to Dr. Agon's own personal interests than anything he could do in a hospital. The company wants to do anything possible with brains and after that even the impossible.
Today's schedule has Dr. Agon transplanting a brain from a small badger (Mellivora capensi) into a small black squirrel monkey specimen (Saimiri vanzolinii) while the outside world slowly catches up to what is going on in his labs and wants to stop it while he has to show some results for his boss, the investors and his own sanity. At least he thinks this is a bridge step to one day transplant a human brain from one body to a newer and younger body.
He studied all the failed attempts and parameters again, this time it has to work!

Help Dr. Agon get the job done by operating sciencefictionally accurate heavy machinery and solving very complex puzzles. What could possibly go wrong?