Go to Home Depot and check out their masonry department. You'll pretty much need one of everything.

j/k
It's a bitch and a half to work with existing masonry. Since you have a ledge, I'm assuming that there are bricks jutting into the wall. You can dismantle the majority of the ledge with a masonry hammer and chisel, but when you get to the bricks closer to the wall you need to be EXTREMELY careful.
There's no feeling of frustration like breaking a brick off inside the wall.
Get yourself a reciprocating saw with an assload of masonry specific blades. Go slow and careful. Tip: Mist water onto the bricks as you cut. Cuts down the dust that you throw out and keeps things cooler.
Don't worry if you do break off a brick inside, you can usually replace the brick if the ones around it are in good condition.