I have really clear-cut goals, and I make sure they are evaluated routinely -- it's important to me as a nursing administrator to make sure that the managers are "managing". They take too much out of my budget to be screwing up, you know?
The damage that one bad manager can do in three months generally takes a year to fix AFTER a stable replacement has been established. There's no way to really attach a dollar figure to it, but in looking at other statistics -- patient fall rate, med error rate, staff sick call-in rate, OT utilization, patient complaints, patient satisfaction scores -- you can generally spot problems and estimate organizational impact, if you know to expect them and care enough to be watching for them.
As far as staff complaints are concerned... There are always two sides to every story, and in hearing one side of it, you can generally figure out what the other will be. I've told my staff that unless they're willing to document a complaint, they might as well not even tell me about it, because there's nothing I can do unless the correct party starts a paper trail that I can follow. If a complaint isn't worth my follow-up, it isn't worth my hearing-about. I encourage them to keep their own personal notes of "little things that can add up" -- stuff that by itself is piddley but lumped together is significant. My philosophy on that is "Cataloging your information is your job. If it ever should need to become my information, I want it organized and ready for me to do something about. I don't expect you to do it all, don't expect me to do it all."
Since you're new in your role, spend some time looking at historical data from your unit. What are the problems? Where are the errors? What are they? What are your strengths? How aware are your staff members of their strengths and weaknesses? How can you have the most impact on the unit as a whole? Your staff? Your patients?
It's going to be hard work, but it sounds like you're happy with your compensation.