You will need to flash the firmware onto the new chip. The flashing procedure depends on what OS version you have: the very early version of OS 3 (with acrylic clear cover enclosure) has built-in USB serial and you can flash through the microUSB port; later ones (with white injection molded enclosure) do not have built-in USB serial anymore, you will need an external USB serial adapter, such as CH340-based (most inexpensive), FTDI, etc. It does require soldering 4 wires (5V, GND, TX, RX). Internally we use a custom made CH340 programmer, which has a card edge connector that plugs directly into the matching slot at the top of the PCB. Without the custom programmer, you need to solder 4 wires onto the card edge connector pins.