the dimensions of motor cowl are approximately 360x360x380 mm. To mill it from the foam it has been divided to 8 multiple layers with 50 mm thickness each. These layers have been milled separately and then they have been glued together. You can see it on the video here
Please note that the length of the milling tool used has to be slightly more than 50 mm in order to mill 50 mm thick layer of foam. It means that the distance that Z axis of your milling machine must travel has to be more or equal to 50 (layer thickness) + 50 (tool length) + 5 (safe distance above the top of the milled foam layer) = 105 mm. Please check if the Z axis travel distance of your milling machine meets this requirement. I assume the size of your table is bigger than 360x380 mm.
Correction: the maximum travel distance of Z axis has to be actually only 50 + 5 = 55 mm, assuming you have additional free space of 50 mm between the spindle and the top of the foam when the Z axis is at the highest position.
I've used a home made milling machine built per Joe's CNC plans, see www.joescnc.com/album/Joe%27s%2006%20Machines/index.html for more information. It's Mach3 controlled. I could possibly generate the G-Codes for you. That would be 10 files (8 layers of motor cowl and left plus right half of the wheel pant). However, this could turn in a lengthy process as I don't know your exact Mach3 setup. To do so, I'd need to know at least what tool diameter you are going to use. If I remember correctly I've used 8 mm diameter. The foam is easy to shape manually so there is no real need for finishing the surface, roughing is sufficient.
I'm not sure what CAM are you using to generate the tool paths. I believe most of different CAMs support the import of .STL files. There are many CAM packages that can be used, many people use for example Artcam. I've found a nice example of how to convert an existing 3D model to G-code here
In this example a model created in Rhino was used, but STL file would work in exactly the same way.
My paypal email is in my previous response at the end, just replace the "at" and "dot" with "@" and ".". Thank you.