The center chassis assembly is aligned to the bottom of the shell with guide pegs. These pegs will need to slide out of their slots to allow the chassis to be lifted out.

Grip the chassis and pull it towards the top of the shell, uncoupling the guide pegs from the shell.

Use two hands to lift out the chassis to remove it from the shell.

During reassembly:

Make sure neither of the ribbon cables get pinched as you lower the center chassis into the shell.

Use the alignment pegs and cutouts to properly orient the chassis in the shell:

Two pegs on the chassis with cutouts on the bottom of the shell.

Three pegs in the shell with cutouts on the chassis.