How screwed am I?

You are not screwed at all.

Address the axle seal and control arm bushing now.
Then do the valve cover gaskets next time you do plugs.
The rear main and front cover are time consuming jobs. Depending on your budget and time, you might push those back until the problem gets "bad".

 

I had some trouble with a pesky drivers side rear axle seal too. The lip of the seal was resting in the groove between the sleeve and spacer where the wheel bearing stuff is stacked up on the axle shaft. I had to reposition the axle seal out-board a bit to get the lip on a better surface.

I found the problem by putting caliper grease on the axle, installing it and then removing and looking to see where the grease got wiped off. That showed where the lip of the seal was resting.

My understanding is the drivers side axle seal was common for this problem on our trucks

 

Holy crap I'd have to live in another country if I got busted for a valve cover leaking.........

 

Yep, as soon as it stops pissing rain here I intend to jump under the truck and investigate. I am quite sure that the "leaks" they are talking about are so damn slow, it's more like condensation so I will need to verify and check back. Might even go ahead and just do a video with a decent flashlight to document as well. Ill check back in a couple days when the weather gets a bit better.

 

There are UV dyes for different automotive fluids.