Iv been trying to sell my nikon d3000 for awhile, but not really wanting to put it on eBay as i hear horror storys of people saying they never recived items. and im just wanting to upgrade aswell to the D90.
I sold my D90 and Nikon 70-200 2.8 VR on eBay this year (over £1500 worth of stuff) but you need to be really careful. When setting it up I used the bidder options to block anyone with low feedback, with non paying notices, anyone without Paypal etc, basically doing my best to only receive bids from legit buyers. They were then posted with their full value declared via Royal Mail Special Delivery. I was pretty nervous and probably wouldn't do it again, safer to sell to somebody trusted on Talk Photography, here or to one of the companies that deal with second hand stuff.
I've sold some stuff to MPB Photographic as they collect it with their own courier etc, very easy and stress free but obviously you won't get as much for the stuff.