Answer to "Screen became very dark during replace front glass."I guess that depends on what the problem is with the iPad. Powering it off and then turning it back on solved my problem with a very dim display after replacing the LED glass cover. When I restarted the iPad, the LED display was as bright as new.
Answer to "Screen became very dark during replace front glass."Very simple repair. Hold the power button down until the "Slide To Power Off" screen shows up. Give it several seconds to shutdown then push the Power button to restart it. You get a bright screen again.