You will have to let a certified B&O technician do this job – the new DVE has to be programmed for the tv in case. I have never heard of anyone doing this on his own.
Happened twice on my Avant, and I guess it will happen again. I believe the design is too thin and heat slowly kills the DVE. If the set will be on for a long session, remove the back plates.
There is no chance to replace the DVE on your own. It takes several hours for a skilled B&O technician to replace the DVE including reprogramming the set using a computer connected to B&O.
After it is repaired, @beowillie suggested using the pins on the USB connector to drive a tiny heat sink fan internally — at half-voltage so it doesn’t make noise — and “strategically placing” it inside the case. He rather hand-waved verbally on the BeoTalk podcast as to where he shoved it, but apparently with the case open this was obvious?