To finish off this thread, I will relate what I found out. After much research, help from the discussion board (thank you guys!), and several phone calls to a support center, the verdict is in: what I needed to do could not be done.
Linking the structural dwg file into another revit model and then attaching that model to my main model produced no useful results. Either the file came in and was still not cuttable, or it wasn't visible at all. (granted, this one left much room for human error, as I'm still a revit novice and could easily have missed something obvious.)
I also tried to create a family out of the structural drawing, both in place and otherwise. I did get this family to come in to my model, but got an error stating that there were too many apexes and to break the file into pieces. I broke it down several times...the smallest was just 1 classroom-size room, and even that was still "too big" according to revit.
[The support center I called had no trouble testing the family concept with their own files, but ran into the same file-size issue I did when using my project files. Their solution? break up my revit model and remove as many links as possible. While that might have been valid advice back in May, it was too late in the game to consider by November. And it would not have fixed the issue at hand.]
Frustrated and out of time, I gave up. So how did I get the structural info into my sections? I opened the section view and a 3D view cropped and rotated to the same area ( the 3D view showed exactly what I needed, but I couldn't dimension it or export it). In the section view I created some lines. In the 3D view I moved the lines around, snapping them to the structure. Then I went back to the section, turned off the structure and turned on the lines, and exported it to AutoCAD. I used the lines I'd drawn in revit to recreate the structural elements, then added the dimensions. I'm about half done with this task at this point, which means I get to do this about 30 more times. It's incredibly slow and cumbersome, but it's working, and I'm happy to finally be making progress.
AJ