Here's how to replace it: iMac Intel 27" EMC 2639 Display Replacement

Even if you have to pay a bit more, get the correct part to eliminate possible hours or days of hassle. You can also search for these: Part Number: 661-7885, 661-7885-R

You should be able to get it for $500

Ali says it is compatible: http://www.aliexpress.com/item/New-LM270...

There can be minor things such as on this question: LCD panel replacement with different (A2)(C1)(C2)... indexes