All four screws are on the top housing, two at the back and two at the front where the lid comes down, next to theslots where the latch hooks come out to grab the lid. The top cover is really snug so you might have to work a flat blade screwdriver around the seam to pry it up a bit at a time all around, but it will come up and after an inch or two will be free enough to lift off.
When you're taking the lid apart, after you have the top of it removed leave it in the open position to disengage the springs and take the hinge rod out, just makes it a bit easier with the tension off the springs. Then there's just one connector to the fan routed through a hole, if memory serves. I can email you more info if you like.