Humidifiers and Dehumidifiers - Aprilaire 600 Hissing A Lot

I have had this Aprilaire 600 for about 3 years, and never did any maintenance on it, as I did not realize it was recommended to change thepanel. At any rate, this year it has begun to hiss a lot. Also, there is a fine dust all around, that I think comes from the humidifier, and but that seems to have slowed or stopped. Will replacing the panel stop the hissing? It looks to me in the manual like a new panel involves several parts - and may be pricey. Can anyone give me a ballpark price? Is it difficult to change? I am (obviously?) not real handy.
It seems to be working fine outside of the noise.

I think you should call a tech and have him take a look. He can change the panel and show you how so you know for next time. Then if there are any more problems he can take care of it at that time. Ask him to bring you a couple of extra panels on the first trip so you wont get charged an extra fee later. They are not that expensive. Also, ask him to go through the control settings with you so you know how to operate it correctly.

It just one things that gets changed when you change out the panel. The panel has nothing to do with the noise. To me, it sounds like the orfice is plugged up with lime/scale, and the water isn't comming out smoothly.

These panel can be found at hardware stores, or home centers. They are about $20 to $25.