shopify and USPS integration (automatically emailing USPS shipping labels)

USPS integration with Shopify store. Basically, I need when customers purchase service from my Shopify store to receive a Shipping USPS label with my store address so they can simply attach it to the box with their item and drop it in any USPS office. We do not sell physical products, we sell services. Customer send us lets say a jacket, we customize it and send it back to the customer( with a paid returning label from customer at checkout) or customer comes and picks up the jacket from our store once we are done with the service. on the checkout customer can choose 2 options : - ship and pick up - ship and return depending on what they choose is what shipping label will receive in their order confirmation email so they can print it, stick it to the box and it's all done. We are looking for an AUTOMATED way once customer purchase a service and pick a shipping method to receive an email with the USPS shipping label ( depending on what its picked as a shipping method at checkout -with return or without return). If you read my requirements when you contact me to type the word " green" so i know you have read it. please contact me ONLY if you have an answer for it and know how to do it on a Shopify store. Thank you