Printing something the size of a guitar would cost several thousand dollars easily. In that price range you can certainly get a quality scan done as well. To begin with, you can rule out the photo-scanning thing (photogrammetry) because the output has holes and is usually very lumpy and distorted. That might work if you are printing a miniature instrument as a novelty, but would not create an accurate record of the form.
I have tried scanning an instrument (and many other things) with a laser scanner (a hand-carved flute), and the results were ok but not great. The hole sizes and locations were not captured with enough accuracy for a full-size recreation. The spot size of the laser limits feature size, so lasers are better for very large objects.
For professional work I use a structured-light scanner. They capture what is basically a 3D photo, with a very accurate range measurement for each pixel. Multiple range image are aligned and merged to create the final object. Structured-light scanners (also called white-light scanners) typically range in price from $10,000 to $150,000, so you would probably have the parts scanned as a service. On a well calibrated device, you could expect a range accuracy of about 50 microns (2 thousanths of an inch) over a meter, with 0.25mm-0.5mm sample spacing (pixel size). That detail might drop to 100-500 microns or less depending on how well the alignment and reconstruction is done.
Here is a random slice (single view) from a recent body scanning project (I make custom 3D-printed clothes).
Note the texture of the cloth is picked up perfectly. Each scan captures about 1-3 million polygons, and a typical scene or object might take 10-30 scans. This type scanning is also adept at capturing surfaces with variations in brightness, glossiness, translucency, and even fur.
Let me know if you have any other questions.