A good start is having a look at the turtlebot_description package, as this provides a simulated Kinect with only a little bit of overhead - the turtlebot ;) Getting rid of the robot model or copying only the relevant parts should be pretty straightforward.
An example launch file for launching the turtlebot in gazebo can be found in the turtlebot_gazebo package and launched by executing
roslaunch turtlebot_gazebo turtlebot_empty_world.launch
/Update:
The simulated kinect rgb image is then published on the "/camera/image_raw" topic and the point cloud is published on the "/camera/depth/points" topic. These topic names are set in the turtlebot_description/urdf/gazebo.urdf.xacro xacro macro and can be changed when you setup your own simulated kinect. Note that the simulated Kinect currently does not provide RGB data for the point cloud.