Screen is half black and half grey

This is an old question and the answer is just for completion sake.

Here you get the help and guides you need to repair it yourself. iFixit empowers you to repair your own and save your hard earned money. Use something like this video combined with this guide Amazon Kindle DX LCDの交換 to get to the LCD. Replacements are still available but are getting more and more expensive as the Kindle DX is no longer a very popular eReader. Places like this still sell them but may take a couple of weeks to get this delivered.