I’ve engraved 10 ft x 4 ft images on clear acrylic, and had only a 14 meg file that turned out perfectly adequately. Took ages, but looked great.
100 meg is unnecessary, especially for somethng as small as a guitar!
Our other laser is a little ULS, and it has only 4 meg of ram, and you can still engrave pictures about 12 x 24 inch, if you edit them to not be too big- and they look terrific.
It does take some understanding of processes and limits though.