I appreciate both of your comments and assistance - the video (despite being in French) did lead me to understand how to accomplish the process.
However, I confess that I am rather disappointed with C1's DAM capabilities, and also am seeing some randomly odd behaviors. So I feel I am not going to migrate from Aperture to C1.
To the former, I have Aperture "projects" that span multiple years - for instance, there is one for the beach. I return to the beach (or wherever) at various times and import the (referenced) images into the same "Beach" project...so at this point I have images there from 2008 to last month. Likewise with other projects. I also had created smart albums in Aperture (all of which I deleted before importing into C1 as per instructions), but when I tried to re-create them in C1 they sometimes worked, sometimes not. For instance, when I used a filter so one album grabs shots dated 1/2015, a second for 2/15, one for 3/15, etc., and while the January and February albums "found" all the appropriate images the March smart album did not. And no, there was nothing wrong with the timestamp in the EXIF files, and yes, those same images were found in Aperture earlier.
The other issue has to do with keywords... in Aperture all 50K images are in one library, strewn across various folders/projects etc. And if I want to make a smart album for all images, from any project, where the keyword is "groovy" (or whatever), the Aperture will indeed find all the images from across all those projects with the appropriate keyword. I see no way to do this in C1, as each project (or session, I presume) seems to stand alone.
To the latter, when I sent into the "simple" tab of the color editor to do that red-eye dance, it sometimes was just black and did not allow me to use the sliders. I could not correlate this behavior with anything else - what layer I selected, whether or not the color picker was "on", etc. Rather frustrating, to say the least.
So, thus far, while I like the layer capabilities and certainly the RAW renders are quite nice, for my purposes it just doesn't seem to be the right tool. Ill keep playing with it and watching videos, but I am not hopeful.
Regardless, thank you for your help.