Plunge deep into the caulk lines encasing the damaged acrylic block with a utility knife. Make the cuts on both sides of the acrylic block wall.
Break the block by hitting it with a rubber mallet. Take care not to damage the surrounding blocks. Dislodge smaller pieces with pliers until you have removed most of the face. Continue by doing the same on the other side.
Take out 1 inch of the block's left and right walls with a hacksaw. Stop when you reach the lines you cut in the caulking. Pull the top and bottom sections of the block out and away.
Cut away at the eight white clips at the corners of the back and front faces with a utility knife. Continue till the clip's housings have even surfaces. Cut away any other leftover plastic or caulking to leave a clean opening.
Install the new replacement block into the space you created so that it lines up with its neighboring blocks. Tap it into place with a rubber mallet. Check that the surface is level.
Apply a line of caulk with a caulking gun around the repair block. This will fill in the cuts you made before in the caulking.