Black screen

- try booting in Target Disk mode (reboot and hold down T key while booting), then connect via firewire to another Mac - see if you can mount your MBP hard disk on that other Mac. If so, immediately back up your important data from your MBP

if it doesn't even do that, you may have damaged your logic board. You can likely still save/backup your data if you take apart your MBP and remove your hard disk, then either install it in an external drive enclosure, our use a universal USB drive adapter, like this one

the fact that you don't even get a display on an external monitor is a bit worrisome and also may point to logic board damage. but before making that conclusion, try a few other things...

you could try reseating all the RAM modules, although if they were simply knocked loose, the machine would likely show some other signs of life. you could also open up your MBP using the guides here on ifixit.com and see if there are obvious signs of connectors that may have been knocked loose.

if you notice any other symptoms, report back here an we can try to help diagnose further. good luck