Since replacing the part I cannot register on the network, Wifi works, cellular says full signal but selected network unavailable. Sim works in another phone and another sim doesn't work in this phone.

This guide may have been written for a different revision but the SM-G900F that I just repaired had glue sticking the entire of the rear of the screen to the chassis making it very difficult to remove. Had to use a spudger and push it down the inside of the phone separating the copper film from the chassis to free it up. Would be easy to damage the home button cable but I was ok.