Some dampers are rebuildable, some aren't. The amount of oil inside one would be tiny, there's only around 2.5 ounces of oil in each rear shock so a steering damper would hold maybe an ounce on a good day, if that. 
If you're lucky enough to own a rebuildable steering damper then I'd recommend that you do so, but as I've said previously, if your damper isn't working as it should, bin it, even a cheap non-rebuildable damper is better than a "quality" one that doesn't work. Cheers, Terry.