For a newly arrived Haworthia, proper treatment not only help it adapt to the new environment more quickly but also avoids possible major maintenance in the future. The most immediate and most important thing is to quarantine it by keeping a good distance from other plants to prevent pest infestation. And the remaining other work can then be done gradually for the next few weeks.
Clean as much of the growing medium out of the roots, even this may tear off some roots. The removed growing medium should be discarded. Further, flush the roots in running water to remove dust. Soak the plant in a potassium fatty acids solution to kill some commonly found pests like mealybug. After that, let the plant dry out in a cool and shaded place for ~2 days before the next step.
Inspect the plant for other pests like aloe mite and treat accordingly. Prune roots if applicable. After finally planting in the growing medium, keep the plant in a shaded place to help the roots establish. After a few weeks, apply Imidacloprid to increase its resistance to common pests.