Ear piece doesn't work

There are a number of things that can cause this, but the most likely is that the flexible PCB that connects the flip to the main board is damaged. It's not hard to replace, but it does require you to substantially dismantle the phone - it's the part that's threaded through the hinge in lower section of this photo.
The only tool you need to open a K1 is a T5 torx driver - you will also need some narrow double sided tape to stick the bezel back on the flip, since you have to pull it off to expose the screws.