To answer your question's, the IS-F will not shift Up or Down if your in Manual Mode. It is designed to work just like a traditional Standard Transmission would. This is great for people that like to run the car hard on a track and make sure the transmission does not override them and suddenly they are in the wrong grear. This allows the driver to "bounce" off the rev limiter if needed/wanted.
As far as changing the oil yourself, you can, but is not recommended.
As far as changing the oil yourself, you can, but is not recommended.