Using a raspberry pi 3 model B, V2, I had been using the serial port assigned to GPIO pins 14 and 15 (TXD0 and RXD0) to connect to an XBee radio and transmit data from a few sensors. This has been working perfectly, but some hardware issues on the prototyping board that will be on top of the raspberry pi 3 have made GPIO 14 unusable on the prototyping board. The pin on the raspberry pi is fine, but I can't connect to it using the prototyping board. I could always remake the entire circuit on a new prototyping board, but I'd like that to be a last resort.
Is there an easy-ish way to reassign the pins that do specific jobs? Could I tell the raspberry pi to treat the physical pin GPIO 21, or whatever, as TXD0 instead of GPIO 14?
I'd appreciate a very novice-level walkthrough as I'm pretty new to all of this.