After a few months of punting, I finally configured Sphinx search on our dev box this afternoon. All in all, it took two hours to install, configure, and add to our tech WordPress theme. Here are my original notes if you want to try; if you install with a package manager, the greatest difficulty is understanding how to tune it and integrate into WordPress search. Next steps: refine search interface/experience, configure usage monitoring, add to corpus of data, rinse and repeat. Just think of how much more empowered educators would be if they had access to student search treads.