Kernel #9 is supplied with 1.02/1.05 live at the moment. Kernel #27 has more features, but it seems it supports less wifi adapters, so it will not be installed by default.
The power off & eject feature should work with any kernel - it's just a user script that does the work. Martin_L was using it with kernel 27, and was also testing the DEEP_SLEEP feature (which kernel #9 supports differently than kernel 27).
So, IMHO, you don't need to change kernels for this feature. Give it a try as it is (enable it first in the webend).
If you want to change kernels and use IPv6/iptables for instance, you can install kernel 27 by overwriting the wdtvlive.fff file with the one in svn (
http://svn.wdlxtv.com/filedetails.php?repname=kernels&path=%2Flive-ipv6%2Fwdtvlive.fff). Then you force a firmware reflash and the new kernel will be installed in place. You just need to edit the ver file to pretend you're installing a newer firmware...