The combiner box's function combines the solar panels' strings into a single box. Each string is connected to a fuse terminal, and its output is combined into a single cable that connects to the inverter box.
You can replace your home's electrical panel on your own if you have some electrical knowledge and skills. It is critical to take precautions, have the proper tools, and understand how to replace a panel. If you are unfamiliar with electrical work, it is best to contact a professional Electrician.