Yes, you must omit the "on". It's ungrammatical to leave it there.
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PreciousJonesYou will see the consultant first and she will sell to you what to do on your face. After that you will see the doctor, and lastly the consultant again to discuss on the pricing.sell to you ... on your face? How about 'advise you what to have done with your face'? That seems better to me.