You will need to chroot again and post your /boot/grub/grub.conf
did you use genkernel or manually configure your kernel?
Hang in there it is very fixable,it is one of the first learning experiences of gentoo.
One time I forgot to set a root password so when I booted up and went to log in I hit myself in the jaw went I realized what I had done.You can use this guide;
Activate the swap partition) # swapon /dev/hdax
(Mount the root partition) # mount /dev/hdax /mnt/gentoo
(Create the boot mountpoint) # mkdir /mnt/gentoo/boot
(Mount the boot partition) # mount /dev/hdax /mnt/gentoo/boot
(Go to the mountpoint) # cd /mnt/gentoo
(Extract a stage tarball...) # tar -xvjpf /mnt/cdrom/stages/stage<your stage>.tar.bz2
(or download the latest tarball...)
# links http://www.gentoo.org/main/en/mirrors.xml
( ... and extract) # tar -xvjpf stage<your stage>.tar.bz2
(Optional: unpack a portage tree)# tar -xvjf /mnt/cdrom/snapshots/portage-*.tar.bz2 \
(Optional: copy over distfiles) # cd /mnt/gentoo/usr/portage; mkdir distfiles;
# cp /mnt/cdrom/distfiles/* distfiles/
(Select a mirror) # mirrorselect -a -s4 -o | grep 'GENTOO_MIRRORS=' \
(Copy over nameserver information)
# cp -L /etc/resolv.conf /mnt/gentoo/etc/resolv.conf
(Mount the proc filesystem) # mount -t proc none /mnt/gentoo/proc
(Chroot into the new environment)# chroot /mnt/gentoo /bin/bash
(Load the necessary variables) # env-update; source /etc/profile
(Network-only, non-GRP: update Portage)
# emerge --sync
Just do the mount and chroot stuff,you just need to get in there.
I could have edited it but I'm tired.