You shouldn't cut them!
they are filled with fluid/gas and if its released it will become effectively useless
best bet is to find a smaller heat sink, or modify case
also, if you are being shocked they you have other serous issues!
So if the top panel isn't on, the computer works perfectly?
Did the case come with a power supply? Because, computers run off 12v, and that shouldn't be enough to feel a shock, so either somehow you are getting AC (120v) leaking, or something is making static buildup
did you make sure that no part of the mobo is touching the case that shouldn't be? no stray wires?
The case didn't come with a PSU i bought a corsair cx430. I actually bent the bronze heatsnks. When I first put the side panel on it casused them to bend a little, so I got some pliars and bent them more. This caused one of them to actually crack. I didn't notice any fluid though. Yes it runs without the side panel, but when i put it on it causes the error