Disassembling the Xbox 360 Slim™ console is tough and a pain to work with. A lot of gamers broke their console trying to disassemble the Slim and XCM are now releasing an X8 Unlock Tool Set (total of 8 pieces with special made screwdrivers) for opening Xbox 360 Slim™ consoles. It will be quite easy to open the Slim console with the correct set of tools now.
Release will be soon and I would predict the price for this kit to be around the $20 range. In the meantime, get familiar on how to disassemble the Xbox 360 Slim by watching the video: