2005 yukon will not start on first try

I would take your mechanics advice and replace the fuel filter at the same time.

There is no fuel pressure sensor on the 2005 Yukon. The pump has a check valve in it to keep fuel from running down the line and back into the tank. If the line drains then there will be no pressure in the line at startup even though the fuel pump does prime. When you turn the key on but don't crank it the pump will run for two seconds. to pressurize the system. If the lines are empty this wont be enough time to get fuel pressure up enough to start the vehicle. And not many people turn the key and wait two seconds before cranking the engine. The best way to verify a bad check valve, (which is very common on higher mileage vehicles) is to turn the key to run, wait two or three seconds. turn the key off, then back on again. Wait a few seconds and start the truck. If it starts right away, you have a bad check valve.

or leaking injectors

7is there another way around startung my 2005 Yukon with out the yetc b:ç I qipecac

I have a GMC 2005 yukon that was running find til it didnt want to drive in D but only in R. So we changed the transmission and now it doesnt want to start at all. We check why was the reason and the code P0355 poped up so we changed that and still doesnt want to start we check P0107 we havent fix taht yet. My question is that why isnt it starting if it was fine starting before we changed the transmission.. please help and thank you