The History mechanism works by keeping a surface you create with a curve "Attached" or "bound" to that curve. After the surface has been created, you can edit the curve and the surface will "Updtae" to the new shape. YOu can see this happen in the Video tutorial "Six Legged Pod" done by
Michael.

When you use extrude, it will go in the direction you point starting from the object you are extruding. The dialogue provides a means to set direction and a path also. Your letters actually start from the base of the buckle and go up through the top of the surface. If you Boolean Union them together they will become one piece. and the Letters will be .125 tall off the surfase they sit on.

There is an add-on script that can tell you distances that I like to use for "Probing".

If you go to the MoI home page, look at the resources tab, then follow the link to Petr's MoI page, you'll find a script called "Custom Distance". THere should be good instructions on how to install and use it. Post back if you need help with that.
Burr