Here you go. I knew one was out there.
http://www.a1sewingmachine.com/manuals/66.pdf
In my opinion, the only thing to be afraid of is the wiring on the e machines. I have a vintage 128 and I sewed with a little trepidation the first time, but the wiring is all original and there was no problem. If you want an exact 66 model or age, post the serial number or go to the Singer site.