does your surveyor have experience with Sabre in particular...what you have described is a known issue with many Sabres. On my 38, the laminated block was replaced with an epoxy coated piece of hardwood, and a steel plate on top. YOu will need to make sure that this piece is correctly made, installed and sealed, else it will re-appear. The 28's are very similar, smaller.
If this has been completed correctly, then you merely need to repair/replace the sole itself. Once the backing has been wet and not dried correctly, you almost need to replace (it is easier) SOme replace with synthetic teak, others use an epoxy coated marine plywood and attach veneer, teak, holly, cherry, mahogany, etc and then finish. To match to the existing curved sole, that is likely 20+ years old, you will need to find a true craftsman, boat carpenter and someone who knows Sabre...
All the best..btw, the solution is to seal the mast step/partners, open or add limber holes to the sump where the step sits and make sure that any leaks are corrected...