the hood is attached to the frame before assembly, i think. the two pegs that hold the hinged part of the top are actually inserted from underneath, then the top is siliconed to the aquarium.
i have a little dremel tool and some plastic bonding stuff, i was going to carefully saw off the pegs that hold the top on and just reglue them.
but i decided against that. it's easier to use a drill or dremel to modify the parts where the cords come out through the hood, and fit a new cord in that way, rather than trying to take the top off...
did that help? are the cords the problem in your way? if not, what makes you need to take the top off? explain more. i was able to fit the heater and new pump by simply opening the lid and tossing them in. the heater is one of the little low wattage submersible things. the pump is a MJ600, it just fits perfectly!