Today when I started sewing my Helga sounded so terrible that I thought that was it. Then I realized it's been ages since she had her dusting day. I do it always by myself. I used to take my machines to repairman; to several ones. But they never satisfied me and my needs. Sometimes the machine came back as dusty as left. So at the end I saw no reason to pay for it that someone just looks at it and says "job done". That's why sewing machine is still the only machine I can fix.
Usually proper dusting helps in every trouble. I remove some parts to get deeper. If you do it for the 1st time take pictures from every step so you can put it all back like it supposed to be. Proper dusting and vacuuming make miracles.
At the shops they sell all kind of aerosols that blow the dust away. More expencive they get if there is written sewing or craft on the bottle. Proper vacuuming by every women's best friend does the same. Just be sure there's nothing important that can dissappear into the depths of the machine... That is not fun.