P0449 Then P0455, 2003 1500

[balingwire]

The SES light on my 2003 Chevy Z71 extended cab (5.3L, 120,000 miles) just started coming on (P0449). My first attempt to fix, I pulled the evap vent solenoid from the top of the front of my tank between the cab and bed, then disassembled, cleaned, sealed, and put back in. No code/light for about 2 days, then it came back on (P0449). Bought a new fuel cap from the dealer, no code/light for 4 days, then the light comes back on today (P0455). Do I need the ACDelco 2142081 part? Should this fix it? Does this part relocated the solenoid? Do I also need to replace my vapor canister? It is in front of the tank now. Will I need to relocate it to the side of the tank? Thank you for the help.