Its extremely simple you just have to unlock the bootloader (which is also very easy) and that wipes everything on your phone.If you wish to unlock and flash a kernel here are some links to watch a video.
First you need to unlock the bootloader/root/install clockwork, lucky all done in 1 easy step. Unlock Tool, just watch the youtube video should explain everything.
After that all you need to do is download the Zip file for the kernel, place it in your phone, restart in recovery mode, then select flash zip, sd card, and locate the file. That is all there is too it.
I have found Franco Kernel to offer great battery life and he is really trying to control how the CPU works for gaming and non gaming tasks to optimize for performance, battery life and heat.
All the best and if anything comes up their are many kind people here to help.
Thanks for the detailed reply, I'll get on it. Does putting on a new kernel void the warranty ?.
Its relativity easy but if your phone is not already rooted. It will wipe all the data when you root. Head over to XDA to find out how to root.
My drain on idle is about 1% per hour on 3G, less on Wi-Fi. But the culprit could be an app draining your battery.
Yeah my phone isn't rooted so I'll backup my apps first and transfer them to my PC.