As I said above, in a post that's then been misquoted as saying the train only needs a clean, all of the parts needed will most likely already be in depot stores, except perhaps the door under the perch seat but I've seen them fabricated on demand before. I'd be very surprised if it couldn't be done within standard depot resources, albeit perhaps increasing the overtime bill.
The biggest job will be the windows, unless any of the shunting controls have been damaged inside the shunting cabinet under the perch seat. Some depots can't do glass work in house and need contractors to come in and do it. However, I've seen them go for an entire door replacement in the past as it was quicker.