Brake Proportioning Valve Rebuild?

[Ram50-Newb]

So the truck is just about road worthy. Was preparing for inspection and noticed the master brake cylinder was leaking, so the brakes were squishy. Swapped out, bled the system took it for drive and noticed they were better but not good. Climbed underneath and found moisture on the proportioning valve. Connections seem tight, so thinking rubber gasket failure.

My question, since they are near impossible to find online has anyone attempted tearing it down to replace the internals?
If so, any tips. I don't want to go this route and ruin the only one I have. Because I can't find a replacement.

Thanks in advance.