Now that is really a good one! :doh:
The tutorial you linked to your post not only includes detailed step by step instructions, but actually includes all the necessary links for all the tools and for all the firmwares you'll ever need!
Is it too much to ask that you actually click on the links they provided in their tutorial ... you know, those which actually say "HERE"??? :eek:
Having said that, step 3 of their tutorial will probably not work. If you attempt to directly use the ATAPI.iHAS624_B.GL27.stock.exe flasher, it will probably give you an error message saying that you're trying to flash the wrong drive, or something along the lines of target not found.
What you have to do instead is to flash your drive using the Flash Utility: press the 'Write Flash' button, load the ATAPI.iHAS624_B.GL27.stock.exe firmware file you downloaded from C0deKing's site and then click OK when asked, in order to crossflash your drive.