ChainSaw90, your G53 saying the max resolution of 1366x768 at 120 Hz means good news-
your native monitor/screen is still 3D-capable.. Any resolution with lower than 120 Hz means it's a non-3D.
Now, we can narrow down the cause of the problem a bit..
Can you still remember your G53's BIOS version that was working with 3D Mode
before you had that RMA? Is the BIOS version still the same currently?
You may find the current BIOS version by typing "System Information" in Windows' Start Menu search box.
(It should be there in BIOS Version/Date.) If the BIOS version is outdated, try updating it with EasyFlash.
This may help with the ROG button functioning as 3D on/off toggle.
However, I'm still confused as to why your nVidia Control Panel doesn't have the "Stereoscopic 3D Settings",
assuming that you installed new nVidia driver version correctly. In fact, any of of the nVidia drivers
(from the stock nVidia driver that initially came with your G53, until the latest one now) should have
that 3D functionality as a choice, during installation.
Perhaps, you might want to do this nVidia driver installation procedure?:
(Disregard if you this already)
-Uninstall all the nVidia drivers in Windows Programs and Features (multiple restarts are expected).
-Reboot in Safe Mode (F8), use CCleaner and Driver Sweeper to clean previous registry remnants.
-Reboot in Safe Mode again, install the newer WHQL driver. Choose "Custom Installation",
make sure all are checked except maybe "nVidia Update". Reboot.
ASUS G74SX-3DE