Crashed my drone, broke the yaw arm & tore the ribbon. I just finished replacing all that & powered the drone on only to find that I'm getting an esc error. It states that it's on motor #1, so I'm hoping it's just a motor swap. My question is, which motor is No.1?

Hello there cadet. I am sorry to read and to know that your DJI Phantom 4 Advanced crashed and for the inquiry. Kindly please refere to the post of JetSam on post #2 where the motor of the said drone is located. In addition, since there was a crash happened I would recommend you to contact our DJI support team at https://www.dji.com/support?site=brandsite&from=nav for further assistance. We have a professional team that will do there best to check the said drone and will give out the best resolution for this issue. Just a reminder that  DJI do not recommend doing a DIY in fixing the said DJI drone to avoid further damaging the said unit. Again I am sorry for the trouble and thank you for your understanding.