Lower left part of backlight dimmed

Since a couple of months I've noticed that the backlight of my 27" Mid-2011 iMac was blinking slowly and iregularly.

Today it doesn't blink anymore but there is a big part at the left bottom which is now a little bit darker than the rest of the screen.

The content is still well-readable but there certainly is some backlight missing.

It doesn't show too much however because OSX has those semi transparent background stuff and in combination with the Yosemite backgrounds the issue is a bit hidden from plain sight. Changing to an all-white background though shows clearly what's wrong.

Are these backlight things changeable - or better - serviceable? There is no Apple store or service center around without boarding a plane.

I wasn't keen on opening the iMac - certainly because I didn't have the sucker tools, but managed to do it without. Dirt easy with the ifixit step by step guides.

I was quite sure the 4 year old beast would be full of dust and rust, but it actually turned up to be cleaner than any computer I've opened up in my life. Just a little rust on the big middle iron piece and some minor dust on the 2 fans.

Closed it down, dark screen, opened it back up and reinserted all connectors, got white screen during startup and now I'm back in OSX back to step zero.

I'm not sad I opened her up though - it was a nice experience!