Proper treatment of a new Haworthia not only helps it adapt more quickly, but also can avoid major maintenance work in the future. The most immediate thing is to quarantine it, keeping a good distance from others to prevent pest infestation. The rest of the work can be done gradually in the next weeks.
It is recommended to discard the original growing medium. Clean as much of the growing medium out of the roots, even this may tear off some roots. Flush the roots in running water to remove any dust. Soak the plant in a potassium fatty acid solution to kill some commonly found pests like mealybug. After that, let the plant dry out in a cool and shaded place for a few days.
Inspect the plant for other pests like aloe mites. Prune roots if needed. After planting in the new growing medium, following the rooting process to let roots establish. After a few weeks, apply Imidacloprid to increase its resistance to common pests.