i too backed into a tree and broke my passenger side lense thats in the bumper. the right bumper piece itself was mangled and broken off the clips, but i managed to take it apart and put it make on with not much problem. i basically started by taking the mudflap off, then took the bolts underneath the bumper out, and then the 5-6 bolts that run along the top of the bumper that are inside the hatch. like when you open the hatch theres a row of bolts that run along the top of the bumper. its actaully very easy to do if you just crawl around and look for everything
there are clips and "cusions" that are inside the bumper, and most likely you broke the clips..
if you happen to find repair parts (preferably a lense) let me know because i cant really find anything cheap
<a href="http://www.trademotion.com/partlocator/index.cfm?action=getJointLocator&siteid=840&chapter=ARM8416§ionids=,2836&make=34&model=4runner&year=2004&catalogid=2&displayCatalogid=0"> this should help you see all that the bumper includes </a href>