it looks like we really should have a kernel upgrade howto somewhere
1)download the kernels and install like any other package.
You will need the kernel and kernel-module packages, the kernel-src package is optional and only needed to build kernel and drivers
2)update your bootloader to add the new kernel, this can be done easily with vliloconf
3)install any extra driver packages needed by your system, these can be found by searching for the old kernel version in /var/log/packages
root:$ ls /var/log/packages/*220.127.116.11*
4)run depmod to update the kernel module dependancies
root:$ depmod -aq 18.104.22.168
depmod needs to be ran with the new kernels version as an argument or ran under the kernel you want the modules updated for.
5)reboot into the new kernel and verify that it is working correctly
run "depmod -aq" and reboot if not ran in lest step
This would include making sure your video driver was working and that you compiled a driver for the running kernel if needed.
6)remove old kernel and driver packages with removepkg
be careful not to remove the kernel-headers package even if it looks like an old version