i have a standard plane created with unity and replaced its mesh filter (that had 121 tri, 202 vertices) with a mesh filter made in blender that has 2 tri/4 vertices.
if i set the material up with a texture, i get only a very small portion of the texture drawn on the plane. How can i draw the full texture on the new plane?
You need to adjust your UV mapping so that the 4 vertices cover the whole image. Take a look at the this demo file especially at the UV scene layout.