Blotchy render and not rendering whole mesh?

Hello. I am new to blender and have started on my first major project, a 1969 Dodge Charger. When I render it I can see the polys on the model and the whole mesh isn’t rendering. Here is a picture to show you what I mean.

If you can see the mesh has stopped rendering at the glass and in the engine bay you can see the polygons. My mesh is very high poly, fully detailed interior, enginebay and undercarriage so is that a problem or not?

EDIT: and can I make my render any higher resolution, as you can see it’s a bit blurry.

Check in the outliner window to see if you have disabled rendering for any of the objects.
Check you have not used render layers to control what is/isn’t rendered
Increase the render dimensions in the render panel.

Also checking the camera falloff (depth of field?).

About the blur, antializing…or however you spellit, can change the blur based on mode and amount.

Your camera clipping may be too short. Select the camera and in its properties-> Lens panel increase the clipping end value.

The black polys could also be doubled faces.

The black poly’s are supposed to be black. If you look on the left wall of the engine bay you can see poly’s. Could this be because of the mirror properties of my material.

^^^Yes, it looks like the left side of the engine bay has doubled polys. In Edit mode select the engine bay and W->remove doubles. Or in Object mode, see if there’s a duplicate object overlaying that panel. The bumper seems to have the same problem.

Regarding seeing the flat faces, do you have Smoothing turned on for all meshes (T key->smooth), and have you used a subsurf modifier? It looks like you’re using too many polys for this model.

Could be that I have overlaying meshes because I have built it in seperate parts eg. for the engine I starred with the block and worked upwards, but it is probably just doubles. And is there a problem with having my model so high-poly. Blender takes a long time to render scenes a lot less complex than this, they have complex materials though, but in this model I have lots of reflective and chrome materials and it renders in a couple of seconds, so when I get everything done will the high poly count be a problem when I want to render more complicated scenes.

High poly count will affect viewport performance and animation, not so much rendering.