Is it possible to install new drivers when running the frontend from the CD? In particular, I am trying to install the nvidia drivers, because the frontend boots up with the vesa driver. I try following the usual instructions, but end up with errors because of read-only directories and files (makes sense because the CD is a ROM).

As one would expect, I can't get good playback of HD recordings from the CD frontend with the vesa driver. I tried modding the XF86Config-4 file and maually changing the line frome "vesa" to "nv". This helped a little, but not enough.

If you boot using "expert" you'll get a chance to load drivers from a floppy. What you need to do to prepare that floppy with the Nvidia drivers is the question.

If I pass the "expert" command, what am I getting myself into? Will there still be a menu for me to choose "frontend only"?

Yes. The big difference is a few more options along the way.