Great! I will follow up here when the first tutorial is available.
To list the ROS topics available, you may use the rostopic command line tool. For example, the commands could look like:
roslaunch stetch_core stretch_driver.launch
[in a separate terminal]
rostopic list
The roslaunch command line tool will launch the ROS master and StretchBodyNode node, while the rostopic command line tool will print out the active topics at the moment. You may find additional documentation on the rostopic tool on the ROS wiki.