If you can figure out how to open the case you can do the loose wire check. there should be either A) a ribbon cable connected into the motherboard (its obvious that it comes from the screen or B) a connector coming from the screen to the motherboard.
If the LCD is bad it could cost you up to 200 bucks for the part alone… then about 60 in labor to get it fixed.
How old is the computer? and does it have a warranty?
Warranty is up, I bought the computer in 06, I checked for all the loose wires that I could but thats as far as im willing to go before I fuck something epic up. I know it happens but I find it hard to believe that the lcd could go bad after that short of a time.
LCD went on my Dell Inspiron after a little over a year but it didn’t just one day stop working entirely. About 1/3rd of the screen would freeze and if you tapped the side of the LCD it would come back on. It certainly is possible for it to have failed though.
Like Kev said, try hooking it up to a CRT and toggling the function key to switch between the CRT output and the LCD.
EDIT:
If it is the LCD, I got my replacement from these guys: http://stores.ebay.com/Smart-Micro-USA
When I took it apart their replacement was the exact same manufacturer as the OEM Dell one.