Starting with fuel pump. It is located in the tank through the top. i have no information stating otherwise. This is where GM has put the pumps for years now. It is a 1.8 hour job not including the4 drain and fill of tank. I have not ever seen the fule pump located behind wheel well. Sorry. here is the info. If I am wrong, I will opt out and let another expert jump in but... never seen one outside of tank and never heard of one outside tanks either.
Replacement procedures for the Fuel Pump/Fuel Sender Assembly can be found under Fuel Tank Unit, See: Fuel Tank Unit\Service and Repair
No worry :) I thought it was time to retire:) had me fooled. here are the pressure specs per your request
Unsure of click . Is it located in pic? this is the complete t boday and airflow meter