The service manual says to release the tabs, but where are they and how do you release them? Also, when trying to remove the entire top cover, I accidentally removed the top top thing (the thing with the handle) attached to the top cover and cannot reattach it.
Reportedly, it's tricky.
Be careful, take your time, and don't break-off the tabs.
With both side panels removed, you lift the top panel off. The tabs aren't visible but if you pull from the rear, the whole piece will lift out. You need to start lifting up the top panel from where the pull out latch is to release the side panel.
Look at the service manual photos closely and you'll see that the top panel lifts off as one whole piece. You may need to remove the optical drive the first time around.