Messed up model, quads? I think I messed up my model. I read that you have to work with quads but somewhere along the way I messed up and now I have a triangle. Is there anyway to make this triangle a quad or have I messed up my model? 

The shading is messed up in the quad right next to the triangle. Is that because of the triangle?
While Lemon's answer about the shading sounds correct, and use of triangles is a subject that can be debated for hours, I thought I would add some suggestions for adjusting the topology you have.

I see two ways to quickly get rid of the triangle you have highlighted.


Add an edge loop &#9096; CtrlR that will terminate at the triangle. This adds a fourth vertex to the triangle turning it into a quad.





Split the mesh that connects the triangles on each side and add in an extra face loop which adds another triangle that you can merge into a quad. With the vertices selected press V to rip the selected vertices. You can also use &#9095; AltV to rip and fill in one step.