The advice was that images for the book in black & white must be set in grayscale. How hard could that be?
Well, it has been a grueling grind of a week. Lots of questions came up. Where was that image that I used in the text? I couldn't find many on my computer, so I had to search the web (again). What was the image's resolution? Thankfully, all my images were at 300 dots per inch, a standard minimum resolution. But how big could the image be on the page? Most were big enough to go out to the margins (4 1/2 inches wide at 300 dpi = 1350 dots or pixels, I think). If the image wasn't big enough, could I find a bigger, better one? Actually, yes, but this took a lot of research and time. If the image needed fixing, could I do it on my old Photoshop Elements? Yes, I learned how to add to an image by drawing straight lines or ellipses, combine images into one image, and turn images into grayscale. I finished going through each of my 61 images, and added one. I numbered them all and organized them so I can find them again.
It turns out that publishers require the author to do this work, and it is required for self-publishing. So, great advice, and I'm glad this part of the work is done.