[Siouxicide]

I've done a search, read the sticky, etc. I'm getting these codes:

P0451 - evaporative emissions control system pressure sensor range/perf
P0446 - evaporative vent control circuit

1. Have others seen this and is there a simple solution?(I've replaced gas cap already)
2. GMMerlin mentioned vent solenoid, but where is it located on a 2007 Suburban 1500 5.3L? And the canister? Anything else I should be checking? I assume these parts will not be clearly marked.

Thanks in advance.