The dealership is the wrong place to call. Lippert is who you want to talk to. They have a great support organization and will help you figure out what is wrong.
Lippert has an App which provides lots of good information for DIYers.
It helps if you describe, in more detail, the symptoms of your problem. Apparently the slides are partially extended.
I assume you have hydraulic slides that are inop? I say that because the dealer had you change the Trombetta valve which is only used by a hydraulic system.
When you depress the room switch, what do you hear? Does the pump run? Is there a click in the battery area?
What voltage is present? Do you have shore power. Is there 12V to the self-resetting circuit breakers (do a Search here for them) all the way to the pump?
Is there 12V signal power (comes from the switch) to the two solenoids (extend and retract)on the Trombetta valve.
You can run the slide manually by using a drill motor and a 1/4" hex head tool. Peel the sticker off the head of the pump motor to find the connection point. Turning it one way extends and the other way retracts.
Here are some links to PDFs in the MOC Files section that may help:
https://www.montanaowners.com/forums...?do=file&id=60
https://www.montanaowners.com/forums...?do=file&id=50
https://www.montanaowners.com/forums...?do=file&id=23