Use google and try to find a picture that is as straight-on as possible (not at a slight angle like that one appears to be). Then blow it up so that a known measurement (i would use the scale length) is accurate and make your tracing from that.
Only use this method to get the shape right, don't rely on it for any crucial measurements (scale length, width at nut, width at bridge, etc.) Squier's website may have records of those or you may be able to find them elsewhere.
As far as the neck goes - If this is your first attempt at something like this, buying the neck might not be a bad idea. You might be able to find a Mighty Mite neck for less than the Warmoth one. That said, if you're willing to invest the time learning, building a neck is not as difficult as it may first seem. It will be a rewarding experience, although with the money you'll invest in materials and tools for the job it will likely cost more than just buying a pre-fabbed neck. It all depends on whether you intend to make building a regular hobby.