Don't worry, James, I've done that a few times myself!

Regarding the paper, hold the stamp up to a light bulb and view through the stamp from the backside. As Smauggie noted, for vertical laid paper you should see some vertical parallel "white" lines representing lines of paper "thins" caused by the wires used to produce the paper. For wove paper, you should see an array of "white" dots instead of lines.