Replacing damaged bricks
It is a fairly simple job to cut out and replace a damaged brick. In many cases the biggest problem will be finding a replacement brick that matches properly. Many times, the best solution is to cut out the damaged brick in one piece, then turn it around and re-insert it with the damaged face inwards.
The quick and easy method is to simply remove the old brick with a chisel and club hammer, however, this won't work if you want to turn it and re-use it, and also increases the chances of damaging the surrounding area.
A better alternative is to remove the brick by drilling out most of the mortar with a power drill. Done this way there is very little vibration on the wall, and the chances of damaging the wall are thus greatly reduced.
You will need a powerful drill with a hammer action - your little cordless won't work for a job like this. Using a masonry bit that is long enough to reach through the wall, drill as many holes as possible in the mortar that surrounds the damaged brick.
Assuming you drill enough holes, the damaged brick should be loose - if not, a few gentle taps on the remaining mortar with a bolster chisel and heavy hammer will set it free.
Remove the brick, then use the bolster chisel and hammer to gently remove the remaining mortar. Clean the hole out thoroughly and remove all debris, then wet the surrounding area with water - this will prevent the other bricks in the wall from absorbing all the moisture from the mortar.
Using a suitable trowel, apply a bed of mortar to the bottom and sides of the hole, and also to the top and sides of the brick. Carefully push the brick into the hole, ensuring that it is level and square with the others.
If the brick is not level, press more mortar into the joints with a trowel. Point the brick and leave to set.