Needing Advice: Navigation Unit Screen went black!

Hi all,
I'm a newbie here! I love my 2012 Prius V wagon.
Gas mileage is superb! Comfort and space is awesome!
My only downside? My Navigation Unit.
Its been replaced once already, but now I may need it replaced again!!
(The 1st time it was replaced was due to the Entune software not accepting an upgrade... 9 months after purchase. The "extended warranty" covered it THEN. But guess what? Back then, the dealership did not follow warranty protocol and now I have a model number that is "not covered"????? What a predicament)

Well, here is what's going on NOW:
In January I had it "detailed" inside, at a local business. Afterwards, the screen "flickered" and went "gray" as I drove away from the shop. Why, you could even see a "water stain" slowly moving across the screen and then "water spots" within the hour! So now the screen is completely dark. Unfortunately, the back-up camera no longer works.
( the xm radio touchscreen controls, oddly enough, still work!! BUT, you must touch the screen and change channels from memory since you can't see the icons on the screen!)

Note: I mentioned before, I had purchased the extended warranty to include the navigation unit.
I have been told, however, that "water damage" is not covered under the warranty as it is not a "manufacturer defect". I have mulled this over for the last 3 weeks. The detailing shop is already on the defensive and has no idea how to fix this problem, despite the fact that they most likely have ruined my navigation unit. Besides...if there was any hope that the actual problem is NOT water damage and the warranty did still apply, he would void the warranty by messing with it anyway.

So my next move is to do the following:
1. Choose the Toyota DEALERSHIP (and NOT the detail/repair shop )
2. Request they REMOVE the navigation unit and INSPECT it carefully and DETERMINE the official cause of the problem.

If this unit DOES have water damage, the replacement cost for a new OEM Navigation Unit per the dealership is estimated to be $4,400 since the "core" would be no good due to water damage.
I refuse to pay that much money for a unit that won't be under additional warranty.

I could seek out a used one.
I could check into a "after market" unit, but how would it affect my backup camera?

Any advice out there?

 

Thanks IMKenNY, I'm having the unit removed on Friday. Will obtain the model number off the unit then. Thanks for the car parts link.....Thanks for your offer as well. Will be in touch.