Hi Rosemarie:
I'm certified by Adobe to teach both applications. I occasionally have InDesign students moving to FrameMaker, and vice versa. Both applications are used for page layout, and while they have similarities (body pages and master pages, paragraph, character and table styles) they have significant differences in how you approach the layout. I suspect he will be a quick learner, but I would still strongly recommend that you send him to training. The freeform approach that works so well in InDesign will be a disaster in FrameMaker.
And because so few people move between the two applications, there aren't a lot of resources like the ones you are asking for. Most users stick with one program or the other. I'm one of two people that I know who uses and teaches both, and I've only had a handful of students make the leap from one to the other. I'm sorry I can't be of more help, but if you have any specific questions, feel free to ask me.
~Barb