Since I am apparently already circumcised (I'm guessing it happened when I was just born, since I have fortunately no memory of it occurring), it wouldn't take much for me to become a Jew if I so chose.
If you want to do it properly (i.e., Orthodox Jewish style), it would just be the matter of lengthy instruction (in the face of active rabbinical discouragement) and completely changing your lifestyle forever to conform with all the minute regulations that a Jewish man is subject to. If at any time between your conversion and your death you are observed to relapse to heathen lifestyle, your conversion is likely to be declared never to have taken place. So, drawing blood from your penis would really be the least of your worries
)