That portion of the expansion valve is not servicable. You will have to replace it to fix the leak. I'm not familiar with your chassis. I am assuming that it is under the dash since you are hesitant to replace it.

If you can see it to determine that it is leaking I would think that it wouldn't be a terribly bad job to replace, but of course, I haven't seen it to know what you're faced with.

Sorry to be the bearer of bad news.

Good luck,