Dpi is a value that tells the printing software how many pixels are printed on one inch of paper (i.e. how big one pixel is on paper).
A 100x100 pixel @100dpi image has exactly the same file content (resolution) as 100x100 @700 dpi image, but on a 300dpi printer the 700 pdi image is less than half an inch wide, when the 100dpi image is 3 inches wide.
A G1 image is 2048x1536 pixels. If you want to print it in 3000 dpi or 72dpi does not affect image resolution at all (it's always 2048x1536), only how big an image you get on paper. Dpi value is only one bit stored in image header, as the camera can not know your printing device it suggests Mac screen display dpi which is 72 dpi - you have top have some value there, 72 is the most used 'dummy' value.
But you must make sure when you resize the image for printing in Photoshop that you UNcheck 'Resample Image' box before you change the dpi to get the required print size. If you don't uncheck the box, you'll be resampling (resizing the image size on disk), which will affect image quality fo good.