Are you sure the port is worn out, as opposed to just getting pocket lint in it which stops the cable engaging fully? Maybe try cleaning it carefully with a fine probe (e.g. a pin, but be careful to keep away from the contacts).
Personally I'd not attempt this. If you've genuinely managed to wear out the port in one year that suggests that LG used a very shoddy part, and so it's unlikely that any replacement will be as bad. But if you really want to you'll need to know what to do with the rest of the USB-C port's contacts: USB-C has 12 (pairs of) contacts, while microUSB has 5, and I don't know whether you can just leave the rest floating. I found a discussion of fitting a USB-C connector to a USB-A device
here, but that's the opposite way round to what you want, and I'd think it's the easier one as the device doesn't have the extra lines.