Ensure that anything attached to your worktop is removed, if this is a kitchen, ensure your water is turned off and disconnect the plumbing to your kitchen sink.
Removing the Old Worktop
Unscrew the worktop using a screwdriver. Using a utility knife, remove the caulk along the back of the worktop against the wall.
Applying the New Worktop
Apply a layer of caulk on the top of the surface the worktop will ne placed. Carefully lay your new worktop in place. Screw it into place using the screws from your previous worktop.
Once set into place you can use caulk along the wall perimeter, smooth the caulk with your finger and allow it to dry.