Here's an update and I think it's good news. I had my machine open for the past few days and I'd peek in at it every time I passed. I disassembled parts that I didn't even know came apart and oiled in there. Learned a thing or two about my machine!! I never did find any thread bits inside even though I searched with a very strong flashlight. But it still squeaked when I turned the handwheel.
So today I did the same as Joe's wife and Tink's Mom - I used it squeak and all. I had 2 small FMQ projects to do today and as I worked I could hear the squeak becoming less prominent and sometimes it went away completely. I guess the oil has worked it's way in or the bit of thread has worked it's way out. IDK!!
Thanks for all the help. Without Tink and Joe saying they didn't wreck their machines by using them, I probably would not have dared to try this. I'll report back again next time I use it. Fingers crossed.....