Original manufacturing in some cases is done by third-parties, alongside development and testing of ride systems.
If you want specific examples, Oceaneering manufactured/manufactures many of the LPS rides (rat, MMRR, etc.), Vekoma manufactures coasters and their trains.
However, Disney does the majority of repair for these. The Everest trains, originally built by Vekoma, can be built from scratch by Central Shops. When I was there this time about a year ago, they were preparing for a rebuild of an Everest train, while finishing up a brand new Barnstormer train.
Not when it comes to Disney's maintenance. The procedure (which I've seen in person) is to strip everything down to individual nuts and bolts, re-machine anything (as in every part) showing enough wear, reassemble, and then test before returning to circulation. Some parts may be bought from vendors, as specialized stuff is a bit more difficult to manage. But even the Kilamanjaro trucks are (for the most part) manufactured in the Central Shops by Disney. The scale at which they do repairs as well as the infrastructure they have for more fabrication is part of what makes them unique in the engineering part of the industry.
Disney is, again, unique in this aspect. While they do buy a quantity from outside companies like Garner Holt, they still do some of their own manufacturing and design of animatronics. A sizable portion of Central Shops is still dedicated to the AA department (And they have a kick-*** sign).
To corroborate, a sizable quantity of foliage/props/decor for pandora was fabricated in Central Shops.
They likely won't produce the original batch. However, they're completely able (and likely going to) repair and rebuild gondolas during their operation.
I didn't mean to have most of these quotes target you,
@danlb_2000. You do some great work on this forum and for this community. But you underestimate the power of Central Shops