The 2010 units come with ContourXD maps. Prior years have Unimap. Mine has Unimap and has the outer contour (no depth) of most lakes and major rivers that I have been on in NY.
You can add Navionics or Lakemaster SD cards, but they are not required to view the internal supplied (Unimap or ContourXD) maps.
Get a gps lock on your position and then use cursor controls to move to the biggest lake in your state. That should be in Unimap. There is a list of lakes that come with ContourXD posted on this site. Pick one of them, if you have a 2010 unit.