I was able to do this on my Mid 2011 iMac without too much difficulty. The actual removal of the glass is really easy as it's held by magnets so no need to worry about glue or anything like that.
Also, after you get your drive installed and try to create your own Fusion Drive volume, you'll need to make a bootable USB drive and boot from that by holding down Option on a boot. If you try to boot from the internal drive and then create the Fusion drive you'll get a "Error: -69879: Couldn't open disk" error which basically means the disk is in use. Of course, when you do this, all your data will be wiped so be sure to backup via Time Machine before you create the Fusion Drive!
It was reversed for me as well. Be sure to verify your own system as you take it apart
When putting the display down on the table, be careful not to kink the flat ribbon cable.