15 minutes - 1 hour
Earpiece speaker was frustratingly quiet, and the battery was starting to wear down to a point that it would run dead before the end of the day.
Removing the front glass panel was the most difficult part, but with some patience once the tool slipped in - everything went smoothly. The earpiece replacement was a breeze, along with the battery. Total time was probably around 30 mins.
Interestingly, I took apart the speaker, and found that the thin membrane around the speaker assembly was partially torn, causing the muted sound. The new was was at least 50% louder.
Patience, I ended up using two pry tools. As soon as I could get one in with an edge, I left it there and used another to release the clips around the glass panel.