In[49]:=

  surface=ContourPlot3D[({x,y,z}-{1,0,0}).uN,{x,0,1},{y,0,2},{z,0,3}];

Pick a point on the surface to hold the unit normal. It just has to satisfy
({x,y,z}-{1,0,0}).uN=0 and be in the first octant.
Recall uN={6/7, 3/7, 2/7}.
How about (0,1,3/2)?

In[50]:=

  np=vectorPlot[{{0,1,3/2}},{{0,1,3/2}+uN}];

In[51]:=

  Show[surface,np];

Up to Example 1