Marble replacement involves removing the old marble and installing a new one. Here are some general steps:

1. Evaluate the Situation: Identify the problem and evaluate the extent of the damage. This will help you determine whether you need to replace all of the marble or just a portion of it.
2. Purchase Marble: Once you have evaluated the situation, you will need to purchase a new piece of marble that matches the existing marble as closely as possible.
3. Remove the Damaged Marble: The next step is to remove the damaged marble. This might involve using a chisel and hammer to carefully break the marble into smaller pieces, starting from the edges. If the marble is being held in place by grout, you’ll have to scrape it off.
4. Prepare the Surface: After removing the old marble, clean the surface thoroughly to remove any dust, debris, or leftover adhesive. If the surface is uneven, you may need to use a leveling compound to make it flat.
5. Measure and Cut the New Marble: Measure the area where the new marble will be placed. Then, using these measurements, cut your new marble to fit. This can be done using a wet saw for precise and clean cuts. Always wear proper safety equipment when cutting marble.
6. Install the New Marble: Apply a thin-set mortar or adhesive designed for the marble to the back of the new marble piece and to the surface where it will be placed. Press the marble onto the adhesive, making sure it’s level and aligned correctly with the surrounding marble.
7. Allow to Dry: Wait for the adhesive to dry completely. This could take anywhere from a few hours to a full day, depending on the specific product used.
8. Seal the Marble: Once the marble is firmly in place and the adhesive has dried, you should seal the marble to protect it from stains and damage. Use a sealant designed for marble, and follow the manufacturer’s instructions for application.
9. Apply Grout: If the replaced marble is a tile among others, apply grout to the seams between the new marble and the existing marble. Be sure to wipe away any excess grout.
10. Clean and Polish: After the grout has dried, clean the area with a soft, damp cloth to remove any grout haze. Finally, polish the marble for a shiny finish.

Remember, marble is a delicate stone that can easily be damaged if not handled properly. If you’re not comfortable doing this job yourself, consider hiring a professional.