Pink and Green Bars; 2010 iMac 27inch

I have a 2010 iMac, 3.2Ghz i3, that i purchased around November time in 2010. Its been a great machine, i use it for school work, video editing for a youtube channel and my day-to-day browsing machine. Since around April last year i have been experiencing some very frustrating problems with it. At first a very faint pink shadow would appear over around 3 inches of my display. I thought, Meh, it dissapears over time; il leave it. Over the course of the next 3months thisarea of the display got darker pink and would fluctuate a little, going a green colour every so often and slowly grew. The next thing i knew (July 2011) I had two, three inch thick bars from the centre of my screen to the left, one pink, one green. I could still view past these bars, and they would slowly dissapear, but they were there non-the less. In November it got to the point where they would not dissapear at all, and were permenant. Text underneath them is almost unreadable, which is horrible for such a high-res display. I have never took the computer apart, the only thing ive done in terms of upgrades is install 8GB of RAM, and that was in November 2011, (After Problem). I understand my Mac is no longer under warranty and i should've reported this sooner, but this has got to be affecting someone else? When i google the problem i see it with 17inch iMacs and Macbook Pros but cannot find any with my case.

Should i take it into the apple store to, and show them, or is this just a write off?

Is it a screen problem, software problem or graphics card problem?

Will this cost anything to repair or is this a known problem with the 2010 iMac displays.

bought this from a local reseller (Comet (http://www.comet.co.uk). Will Apple cover this if it is a known issue with the displays, even though its out of warranty and was sold by a different company?

Thanks; any help would be so amazing!

All the best

JoshLangdon-

PS: heres a quick snap of the display; its not great quality, only tooken with the iPhone4S but still shows what i mean. Hope this helps.