Well for the WHOLE process of modeling you own car, you would need either a blueprint/schematic's of your cars make/model. or a digital camera so you can take photos of your vehicle.
you can look at this
link for reference as to how to setup your camera angles.
basically if you are taking photo's of your car, you will want a side, front, back, (and bottom and top, depending how detailed you want.)
then from your camera take them into photoshop or a photo editing software program, and arrange your photo's to look like the layout they used in the link i supplied above.
Once you have your "reference planes" created in photo editing program, export the image to a png or tiff (you'll want to keep the quality high, i find jpg's are annoying when it comes to reference schematics because of the image compression you lose image details.)
From there, I would probably just follow the tutorial , i looked it over it doesn't look too hard to follow.
Here's a link of
Blueprint database