Don't take a hammer to it!
What is the symptoms you have been experiencing? Maybe it isn't dead yet.
If you were using the internal HDD as the boot drive, there could be a good chance that the HDD is starting to fail. Or maybe it is as simple of a corrupt OS.
You can do an internet recovery and reinstall the OS, preferably to an external drive so not to erase your internal files if that are salvageable.
Those particular iMac models do have a higher than normal chance of GPU failure.
Have you don't an Apple HW diagnostic test? Hold "D" right at the chime during start up.
If you really don't want to fix it or troubleshoot, you could remove the HDD using the HDD replacement instructions from iFixit, it isn't that hard if you have some type of suction cups.
If you have another Mac to use, an easier way to access the drive, assuming it still works, use a Target Disk Mode, hold "T" right at the chime during start up.
Target Disk Mode turns your Mac into an external drive, allowing access to all the internal drive of the Mac by connecting another Mac to it with FireWire or Thunderbolt cable.
Depending on the symptoms, I wouldn't give up on your Nac quite yet, it could be a cheap and simple solution.