[98Expedition10]

Yes you can rebuild several items within the EATC, but in reality I haven't seen many that really needed it.
I did almost exactly what you did for a friends Navi a while ago. He had damage that was mechanical in nature involving the SMT push-buttons, and lights. An exact replacement was somewhat out of the question for my friend (financial problems). Based on a loss-loss situation I decided to remove the EATC to see what was "fixable" inside.
Several of the "O" rings were available in my boxes of rings from air conditioning kits, and even the Home Depot.
Several were refurbished as is using silicone grease from a tune up kit to resurface existing rings and assemblies.
As it was I did fix his EATC including the actual cause of his problems (crimped vacuum lines, plug connections).
The basic problem lies in little available information directly concerning the EATC, Manufacturer preference for replacement option as service. There are Rotunda Service Jigs for diagnostic work, but they are usually unavailable or too expensive for home mechanic service work.
Probably the least expensive method for diagnostic work on a EATC problem would be a unit substitution check.
Good luck on your rebuild.