I have had two crashes and damaged the camera both times. The first one was pretty hard and I didn't want to get into taking the gimbal apart so I bought the whole assembly.
Lots of videos are available to guide you through the swap and I found that it went pretty well. Once you get the shell apart, there are four flat ribbon cable connectors that took a bit of time because they are 'glued' down with a silicone compound. Other than that, four screws and a small plastic connector.
My second crash was not as bad. Like the first instance, the camera still worked after the crash but I got the gimbal overload error. I then bought two ribbon cables and installed them on both gimbals. The first cable replacement took about 3 hours but the second was only about 45 minutes. The first gimbal is still a little off. My guess is that the horizontal motor is binding as that is the motion where the gimbal calibration fails. It works but I have to reboot the Mavic a couple of times to get it to respond. The second cable replacement job went perfectly and every thing works like new.