1) If busbar looks good it probably is good.
Usually when bus is bad, it has burned appearance, and looks like it is ready to crumble or is crumbling.
2) Problem with bad busbar, we sometimes add subpanel next to main box.
Buy subpanel box Home center or electric supply.
Square-D subpanel shown on following page came from electric supply.
http://waterheatertimer.org/How-to-install-a-subpanel.html3) You can also add tandem breaker to main box.
Tandem breaker fits over one bus finger, but is actually two separate breakers.
Then double-up two lightly used circuits so you have room to move breakers around.
See image showing tandem.
http://waterheatertimer.org/images/ap-235-breakers.jpgAdd a comment for more free help.
Also take advantage of fixya expert assistance live.
For a price, expert works with you via e-mail while you work on circuit or any do-it-yourself project.
Fixya is always less expensive than a service call.