Another way to do this is to select the shape and go to Objects - Paths - Offset Path - then enter the amount of offset you want (plus or minus). You will get a new shape with the entered offset.
If you convert the strokes to outlines you get two paths for the stroke you converted (the inside and the outside of the stroke).
If there's a fill you get three paths. Another one centered under the stroke for the fill.
Could not find wireframe on my adobe illustrator tools.Just remember the plotter is only going to cut the wireframe, not any effects added to the design like line weights. Always look at a design in the wireframe to make sure it is not going to need welded, common mistake I see in cut vinyl.