While in robot lab have focused on the simulation side of the subject. I spent the first three or four weeks trying to install player, stage, and gazebo as well as looking at some of the other options available to students for simulation of robotics. Once I installed and learned to use ROS i found that it was not necessary to install player, stage, and gazebo if your going to use ros because ros will do the work for you.
1. installing player
2. installing stage 3. installing gazebo 4. installing ros 5. building robots with URDF 6. building robots with XACRO