Is this a sprint or boost lg marquee?
You can get your phone back up and running. First thing I would try is powering off the phone, Once the phones powered off hold down the volume down button and the power button at the same time, Keep holding until your phone boots into the factory recovery.
Once it boots up into the factory recovery, use the volume rocker to scroll the menu and use the menu as your enter button. You will want to clear catch and factory reset it.
If your phone doesn't boot after doing that, your gonna need to go ahead and install sprint LS855ZV9 software using the KDZ updater and guide outlined on this forum.
It depends on whether your running sprint or not, on how to do the update. The boost phone needs turned on immediately after you hit the update on the kdz updater. The sprint phone you have to wait 10-12 seconds after running the kdz updater to get the update to take.
Once you get the LS855ZV9 software on your phone and your phone is booting again, You will want to go ahead and root the phone, once the phones rooted you can install CWM and from there you can install the proper SW for your phone. Both the boost mobile and sprint SW's are available on these forums.