My battery exploded and made a hole in some plastic in the transmission and now I have water in my transmission

I’ve been out of town for a month. When I got home last week my 2018 Ram Promaster city van (2.4L 9 speed auto) with 20k miles would not start. I had full power for lights. When I opened the hood I found a mess. My battery had exploded and battery acid burned a hole through some plastic parts in my transmission. I took it to the dealership and they said because the battery and some electrical work was done after market they would not cover the electrical problem, but that there was a bigger issue – my transmission was full of water. Prior to this event the van was running and shifting great. The Dealership transmission tech went on to say he did not think that water in my transmission was even related to the battery acid issue but rather suspected it was due to flooding as it had been raining for 5 days straight and slew of jeeps had come in with flooding issues so he presumed my van had also been underwater. However, I assured them I was the only driver of the van that it had never been near water every. They quoted me $8,500 out of pocket to restore the van which included a new transmission. Well, I rejected their not so generous offer, took the van home, removed the battery, rusted tray and cleaned it up. What I found was hole melted through some plastic cover on the transmission and as they stated, water in the transmission. Keep in mind the van has not been driven since the incident occurred over the last month.

Is it possible that water entered through this acid hole on the plastic?

Since I’ve not driven the van since the event, any chance I will be able to fix this without a full rebuild or replacement transmission?