Hi,
Depends where you are! In the UK a used D900 sells for £55-60 on eBay. A replacement LCD is £32 + £4 for a T6 screwdriver, all on eBay - if you can fit it yourself.
I have seen a dead D900 sell for £20 on eBay. It is a swings and roundabouts question. Just make sure you receive good fitting instructions and be very, very careful. Check with your local market shop about the cost before you decide. If you supply the LCD ask them how much to fit it - but they may not guarantee the repair?
Ron Murray, January 2008