"how the upper body comes apart"
With CAUTION and special tools!
First remove 4 screws holding 2 chrome uprights and set handle aside.Remove short inlet hose and cover if newer.
Cover over pivot holds down strong spring and has caution label.Spring should be held down with original tool or make one with bent nail or similar to go in hole beside spring when upper body is fully lowered.Cover should have 2 of 4 screws needing special screwdriver.With cover removed lift upper body and disconnect hose and wires.Then pry off 2 curved metal clips that release 2 small plastic strips that pull outward.It is then similar to the plastic body canister with 2 long strips holding body halves together that pull downward.As with any look,observe,think during these steps and reassembly.
The upper cord hook was meant to rotate and hold 1st 2 feet of cord to keep it from falling down and breaking at rear housing.
Good Luck.