Congrats on getting the 328 up and running! You'll probably like the 66 even better for piecing. I know I prefer straight stitch only machines for quilt work. My 66 was my main machine for quite a while. I've since switched to my Rodney machine and a 1908 model 27 Singer named Ella. They're so much quieter and smoother than most zigzag machines.
The wiring problem can't be too severe. There are a bunch of wiring diagrams in this section explaining how to wire the light and motor. It sounds to me like the light and motor are wired in series with each other instead of being wired in parallel.
Rodney