You can access the top without removing the bottom. In fact, it is easier to do so, so I recommend at least putting it back on (without tightening the screws) and putting it upright.

There are four plastic plugs in the tray for the cups, marked with a triangle (see picture). I used a 3mm (1/8") drill to make a small hole and pulled them out. Unfortunately, I could not find a non-destructive way to remove them.

Green circles: open hole with screw

Red circle: remove plug with drilled hole (just sitting on top of the tray)

Below you find four screws, you'll need to remove. Now lift the entire piece up. The metal area with the thermometer will also lift. Be careful, there is a cable (pipe?) from the thermometer, going to the heating block. You can losen a screw there to remove it. Be careful not to smear the white paste everywhere (you'll want to keep it on there).