most drum brake linings don't tend to wear evenly; the most important thing is that they are clean and free from any oil, fluid, or grease contamination, it would not hurt to get new linings fitted because it doesn't cost the earth and will save time in the long run, check that the brake cylinder piston seals are not leaking any fluid, while you have gone this far you may as well go the whole hog on it rather than a quick fix.Jeremy