I'm really impressed with your repair skills. DJI doesn't seem to care anymore about how easy it's to repair their newer drones as I would rather spend more money to make them easier to repair like the Mavic 2 drones are.
A piece of fishing line looped around the end you need to insert..put the other end thru the hole,, Pull the line till the damper pulls into place.. Carefully cut the wire from the damper. OR- Use some hairspray as a lubricant. any spray that...
Or he was just winding you up because it's extremely unlikely it was what he claimed and the specification he told for the drone and separate camera are likely nonsense as well.
if you don't share the work with your subjects then do the math! I have a lot of respect with my drone work because they get to see what I see with my drone!