Bear

Is it just hard to open, or does it take an effort to close as well? If so, it may be simply that your bar end is on too tight and is causing your grip to get stuck. It may not be this, but a few seconds is all it'll take to check it out.

If you do have to replace the cables, I reckon you could do it without a manual if you're careful and have at least a modicum of common sense. All you need to do really is trace the way they run, run new ones along the same path, then unhook the old ones and hook up the new ones (As far as I know, and the last time I did this was on a 1984 CX500 about 6 years ago!).