We hooked up an OBD11 Auto Scanner to our 2005 Chevy Silverado 1500 pickup and got the codes P0449 and P0455 What do they mean and can we fix it ourselves or do we have to take it in.

P0449 has to do with the Evap System. The problem could be with wiring short circuit, Could be the EVAP canister purge valve or the ECM.
P0455 has to do with the evap system as well. Could be a leak in one of the hoses to the evap system so you need to check all lines to the evap system. There is also one hose that connects to the top of the tank that we have seen come loose. Could also be a intake leak or a problem with the Canister purge valve. You can fix these yourself somewhat. I would trace down all the lines first to see if anything has come loose under the vehicle to the Black plastic EVAP canisters. Without being able to check the valves you will probably have to take it to a shop to have them checked out or pay the price to replace the valves and gamble they are the problem.