zanapsis,
you will need an entirely new bumper cover. the mirko splitter in the BG section is an add on to that SVT part. The splitter only fits on the SVT, so i you want that, you have to get both parts. You can also jus buy the SVT bumper cover. If your looking to make your car look like an SVT, then you will also want to get the side skirts and rear SVT bumper. Micah is workin on a new Group Buy for the rear. I dont know why yuould would only want the front, you car would look funny from the side. Thats just my opinion though...
About the seat height, I dont really know...