The term RocketSurgery is used to mean a difficult task. It is an amalgamation of the terms "rocket science" and "brain surgery".

The phrase "It's not rocket surgery" therefore indicates an easy task.

Amusingly, in one of the StarTrek movies, Spock (Rocket Scientist) and McCoy (Brain Surgeon, at least with some assistance) performed rocket surgery.  Between the two of them, they installed a new sensor (that sniffed out exhaust from a cloaked ship or something like that) into a torpedo as it was going down into its tube.