How can I separate the top (screen) from the bottom (keyboard)?

I have 2 LG Voyager VX 10000S phones. One has a screen issues inside & out and the other has microphone issues. I would like to separate the 2 pieces of each phone & make one well-functioning phone out of the two good pieces. (Would also be open to just using the mic from the bad screen phone to replace the other one if that is easier. Just thought I would prefer not to open & mess with fragile pieces if I don't need to!) Thanks