We need help?

It sounds like the wood will need replacing. Here's a link with a similar problem:

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26403935.cfm

Hello. Starting a new restoration project can be overwhelming. Personally I find a lot of information by Internet searches as well as YouTube videos. YouTube is can be very educational if you can find a project underway very similar as yours.

I would take several pictures of what you have with the siding removed and then as Vimarhonor suggested, Youtube the appearance and structure of your project and see what others have done. Since your trailer is older, there should be something very similar to what you have.

Hmmm, thinking more into it, have you considered taking a look at the other side of the trailer-yup, remove that siding too?

here is more info that may help

https://www.youtube.com/watch?v=CwPHkr74i28

You can also contact the company and see if they have a schematic of the trailer. See what they suggest, and definitely check out you tube.

So the "slight" water damage is severe water damage? Have you contacted the seller? is the sale a done deal? I'd ask for some money back to cover the cost to fix it.

It may have been sold 'as is'.

And, even if the seller was aware of the damage and did not disclose it to the buyer, there would be no way of proving it.

You could post pictures a section at a time for helpful tips on repairing.

Replace with plywood then add siding back