Repairing the Bobbin Winder on a Singer Sewing Machine

I have a Singer Brilliance 6160 sewing machine and I have just started experiencing some problems with the bobbin winding mechanism. On the one hand, the bobbins are not so nicely wound as they used to. I mean, sometimes the winding is not homogeneous and there is more thread at the top or bottom of the bobbin. On the other hand, the machine used to stop when the bobbin was full and now it doesn't. It can continue forever, putting thread even out of the bobbin. Does anyone have had the same issue?
Thank you.

I got this machine, a Singer 7444, brand new. The problem happened very soon after I got it. When I go to wind a bobbin, my machine makes a terrible grinding noise and the sewing needle will continue to rise and fall, though slowly. It seems like something isn't disengaging. One of my neighbors suggested oiling it, but I don't know where or even how to access the parts to oil. Could I have done damage by not looking into the problem sooner? If I go to get it repaired, will it likely be inexpensive?

I am a beginner sewer. I borrowed a machine, a Singer CG 500/550, and somehow the piece that you put the bobbin onto to put thread on the bobbin came unhooked within the machine. I opened the machine up, but have no clue how to connect the piece again. Help?