I have Realtek AC97 audio card and i did the stage3 installation i have coldplug and hotplug but my sound does not work it is one of the problems in my computer i'm about to just give up and go back to mandrake... i cannot get my sound to work nor get my nvidia card installed and i do not know why...
If you used a 2.6 kernel, did you remember to compile alsa and the alsa-drivers as modules (not compile it into the kernel)? If you did, you can just run these commands as root to enable the soundcard:
About the nvidia-card, look here: http://www.gentoo.org/doc/en/nvidia-guide.xml
alsa channels also come muted you can use alsamixer to unmute. If you need a great how-to to guide you here is one.