Hi John,
There is no lens in the front of the telescope.
From photo's I can find of the scope via google, the plastic plug you mention
is a moon filter* is probably a dust cap. You will want to remove this.
The following diagram and page may help you:
http://www.derbyastronomy.org/images...torDiagram.jpg
http://starizona.com/acb/basics/equi...ewtonians.aspx
*Edit: Looking at the photo's again, I think the moon filter is much smaller than it appears in the pictures I found, my guess is it pushes over the eyepieces.