I have a concrete patio that was put in a year ago, but I've since had quite
a few people come in to do work around the house (electrical, drywall,
DirecTV, painters, carpenters, etc). As you can imagine from the sloppy
nature of most of these types of people, the patio suffered a lot of "light
cosmetic damage". Drag marks from ladders, grease stains from air
compressors, scratches, etc. Also, one area of the patio got very little sun
when the patio was installed and seems to have cured badly because there is
a dark stain in that area.

Can this stuff be repaired without tearing it out or putting a skim coat on
it or something of that nature?

I'd be kind of embarrased to call in a concrete cleaning person from the
Penny Saver, because this is a pretty small concrete patio. I'd say in the
low 100 to 200 sq ft. range if that. No one would bother coming out for that
anyways.

I tried laundry detergent and it got off most of the grease stains, but it
still looks bad.

I have a "quartzite" (natural stone) border, so whatever I use should not
damage those.

Also, I live in Southern California, so if it is some kind of coating, it
should not crack in the sun or anything like that.