If all you are getting from the printer is question marks, it sounds like you have communication problems.
Try talking directly to it via HyperTerminal or similar: set the parameters the way the book says, and look for an ID string request or similar. (A quick search gave me "<Esc>*s#^ *" which might report the model number -
http://www.hancockcomputertech.com/blog/2010/05/03/pcl-escape-sequence-reference/[
^])
When you can talk sense from your keyboard and get a readable response, you can move on - but it is pointless until you know you can talk both ways.