Hypothetically, if I were to build a model of my favorite sci-for aircraft but lack the skills to make decals from scratch, would it be possible for me to refer to a model kit's decal sheet, scan it onto my computer, trace each decal in a separate program like Adobe Illustrator as a vector graphic and apply each one to my 3D model?
I agree with "10 Replies": Yes
A vector recreation, saved as high of a resolution png that you need, can be much better than using just a scan. (Unless it's a good scan already, but you'll probably want to cut it out, etc... Still a vector will be noiseless and sharp at any resolution. An exception is if your decals have gradients or many colors-- if it's more like a photo than line art/ clean sharp shapes.)
As mentioned already too, you can't use vectors directly as a texture in Cycles. (But you could at least with the old renderer: https://www.blender.org/forum/viewtopic.php?t=12870 )
But I also agree with Duarte's "Don't bother retracing" comment.
Instead, use a tool like Illustrator's Live Trace, Inkscape's Trace Bitmap, or http://vectormagic.com to save a ton of time. Then you can save your clean, sharp vector as a raster texture to size the you need. Later, if needed, you can make an even higher resolution png texture for your blender render.
A good clean vector file of vector-like art is always preferred to have, even if you can't use it directly as a texture in Blender.
No, don't bother with tracing, Blender can't use vector images as textures directly, don't expect to import them into materials.
You can use the scanned images directly (if they have good quality) or trace them to improve quality, but not to import as vectors.
Blender can import SVG vector files as actual geometry (bezier curves), but can't use them as textures in a material unfortunately.
So unless you want to sanitize them, make the look better by improving quality, or somehow modify them; tracing will be useless, since you can't directly use vector graphics as a texture.
Yes. That would definitely work.
If you do that, you would want to learn about UV unwrapping, texturing, vector tracing, and basic modeling.
Edit: To those of you who think that blenders inability to use vector textures is a hindrance, think again. A vector reconstruction of a "scanned sticker sheet" is going to look a hell of a lot better than raw pixels from a scanned sticker sheet. You can export vector at insanely high resolutions as well, making the fact that blender can't use vector files as textures an insignificant obstacle.