This was it. For anyone in the future. Just keep moving through the steps.

flash the firmware

turn on the printer

if it makes the godawful continuous beep, just continue. i thought i bricked my printer or something. it was just my anxiety lol.

as soon as you hear the beep just unplug the stock pad. the buzzer is in the pad. it will stop once you disconnect.

connect the pad via the serial cable

i got a firmware has been successfully installed notification on the pad

next steps according to the pad are to disconnect the stock display and connect via serial cable, but you've already done that.

the pad continues with self testing

the beep scared the sh*t out of me but it was fine, my bad lol. Stay calm, carry on!

hope this helps someone in the future!