Best option to replace existing 3-way switches

What is the best option to replace existing 3-way switches, if possible with dimmer option.
I bought one aeon labs dsc19103 dimmer but the instructions are not clear for me to proceed with replacement.
I thought this would be the best choice but lack of proper instructions for the install is holding me back.

I prefer to have a dimmer option, but I can live with no-dimmer option too if the install is doable. Do I need to replace both
my switches or can I replace just one? What are the other options available with the install not to complicated?