My wife's Nishiki Landau is having some shifting trouble. I've adjusted these sorts of things on my own a few times. The bike has a suntour derailleur. An ARX I believe. Her problem is that the shifting is sticky until you over shift and then if you go to correct it you'll only need a minor adjustment to get it in gear. Does that diagnosis makesense? So if she's in her highest gear (6 speed) sheel down shift very little and drop 2 gears but then a similar or smaller movement back in the other direction puts her where she wanted. It also jumps gears a bit on it's own while she's pedaling.
I think thats the general problem. I may need to get home and ask her for clarification if you all feel that this can't possibly be whats happening. Anyway, Is it just simple adjustments to the limit screws?