Less than specific!
What did he tell you? Did he mean that the support pin fell down and was sitting above the wash impeller? The wash arm support is screwwed to the pump housing and can only fit in one way and there is no adjustment for the height of it. I have seen the pins loosen up and drop.
IIRC, these were splined shafts that were press fit into the plastic housing. you can probably epoxy it back in place and the unit should work fine again. I have seen these supports sold in various places like eBAY and some of the larger parts distribuitors like Marcone and Repair clinic.
Also, check the washarm itself. There is a bronze bushing in it that goes over the pin sticking up from the support. If there was no wear washer on that pin, the thin plastic that enclosed the bushing would wear away and the the bushing would get pushed out of the top causing severe wobbling and potentially no turning action on the wash arm. If that is the case and you can find the bushing, you can epoxy it in buit do add a stainless steel washer over the shaft and then put the wash arm back. If not, you will need a new arm.
Hope this helps more than the repair guy did!