I am not sure how well kX works with Oblivion, so I cannot comment about that (you would have to try it yourself and see).
Note that kX does not support EAX.
kX install is not difficult, but using kX can be a little complicated (until you understand the kX concept), so you will have to decide whether you want to try kX. See the docs from the following thread:
http://www.driverheaven.net/general-...mentation.html
You should not have to remove the Creative Labs software before installing kX, but things like AudioHQ (driver related stuff) will not work with kX (some of the Creative apps (non-driver related stuff) do work with kX (WaveStudio, etc)). If you just want to try kX, then I would leave the Creative stuff, and then if you decide to remove kX, you *should* be able to go back to the Creative driver by just using the update driver option in Device Manager.
kX does not have any built-in presets for 3.1 audio, but it is possible with kX using a custom DSP config.