I use lilo. I enetered vga=788 for my lilo.conf. Doing a ctrl alt F1 does not work yet. I tried that spacebar, vga=whatever, then enter method you described. Nothing happens at spacebar, and it does not let me enter vga=788.
My lilo.conf file is set for no prompt (I press shift for lilo menu), and automatically set to load KDE. Maybe there is a way to set it up so it loads console mode with the vga=788?
and as a precaution, would there be a way to restore if I completely mess myself up?