Mic is dead, everything else works. call someone and as you speak you hear sidetone

2013 moto x verizon, still on 4.4.2 rooted with towelpie. Everything else works great, but the microphone. Brother said it got hot and than died and wouldn't charge. that was a week ago, now I have it and it charges fine for me and turns on, it factory reset it but when a call is made the person calling hears nothing and i hear my own voice loud and clear fed back through the speaker. Read can take the back off with heat gun and a t3 or t4 driver, can someone describe the procedure a little more, just getting the back off? The phone is in like new condition and works well except that mic. Thanks.

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