I followed this guide to replace my battery - proved to be useful. However, after the performing the replacement, the microphone no longer works. After further testing, the microphone works when on speaker mode, but not when calls are taken via earpiece. Can I get suggestions on what I can do to check for the cause of the issues? Thanks.

Indeed no need to do Steps 6-7 to avoid removing the delicate cable. There is enough space to move the current battery with the cable connection intact.