Saw Zall is the trick unless you want to use brute force and stomp it out witch might cause some cosmetic damage. Best bet is the Saw Zall. You are going to need more than a few little fans to cool off the cab. Do a test run in the cab to check heat before you germ your seeds or you may have another dead grow on your hands.
Hmm after rereading this short apistle I think that if the shelf is connected with some ribits then you might be able to hammer them out. You also might be able to jimmy a flat head screw driver along the brackets and hammer them loose.
Adieu