Turn the BlackBerry upsidedown and remove the battery. It should tell you the model number at the bottom of the battery bay.
There are some places like www.promobility.com
that will sell you a replacement LCD. A replacement LCD will set you back approximately $100.
Please make sure your friend has deleted his @blackberry.net account, and hopefully the BlackBerry is unlocked (unless you plan to use it on the same carrier your friend used it on).
Alternatively, you can sell this broken BlackBerry on eBay, as parts, especially if the BlackBerry is still functioning (i.e. synchronizes just fine) except for the LCD.
The screens are fairly easy to replace on the BlackBerry, assuming you've disassembled and reassembled a computer before - it's a detachable module. Also, you'll need a Torx T6 screwdriver to open up the BlackBerry plastic case. I think the screws holding the BlackBerry LCD down are also the same T6, if I remember right.