Sorry, I just saw a spam before your post, so I thought it was the day 
Again Sorry, and Welcome
Not sure about laser engraving, but for the image processing in GIMP, yes it's quite easy
If I understood, you do need a black and white picture?
GIMP can automatically put your picture in grayscale (you can chose this in the preferences), crop/resize and DPI it's all easy access and DPI can be set to your preferred value as default
adjust brightness, contrast, sharpen, etc manually, or hit the auto button.
All those tools are in "Colors" and in "Filters" also GIMP has even multi "AUto" button
Again Sorry, and Welcome
Not sure about laser engraving, but for the image processing in GIMP, yes it's quite easy
If I understood, you do need a black and white picture?
GIMP can automatically put your picture in grayscale (you can chose this in the preferences), crop/resize and DPI it's all easy access and DPI can be set to your preferred value as default
adjust brightness, contrast, sharpen, etc manually, or hit the auto button.
All those tools are in "Colors" and in "Filters" also GIMP has even multi "AUto" button