If you want to work with what you own, and it is no more than about 3" thick with no steel; you can get masonry cutoff wheels that will fit your skil-saw. Make a groove about 3/8" deep where you want to break the concrete (both sides of trench); then attack it with a sledge hammer. Don't try to work in less than a foot wide.
It makes a lot of dust, but you can try to keep it wetted down. You should have a dust mask.
When it comes to restoring the concrete, I like to mix my own. The SackCrete is always short on sand and cement and it makes for a poor surface. One sack of Type 1 Portland cement, plus GOOD sand and gravel, will make about 5 cubic feet of concrete, which is at least 600 pounds of SackCrete (number of sacks depending on what HD is selling at the moment).