2001 Evap

I have a 2001 Dakota 3.9 Check engine light came on. Checked codes (PO455 and PO442) large and small leak in the evap system. Replaced gas cap and cleared the code. Codes came back later. Need to know my next step? What is the best way to track down this leak? Will it harm engine to run in this condition. Any help will be greatly appreciated. Thanks in advance!!!!!!!

Check the vent lines going from the tank to the charcoal canister making sure they are not cracked or leaking fumes. If they don't have clamps put some on. For smaller vent and vacuum lines, I use wire ties as hose clamps.