I sent out my original passport with required documents to DC. I got renewed MRP passport in 45 days. Be safe, send through UPS or Fedex with return UPS or Fedex tracking method. They will call and inform to you if anything missing or incorrect. Though strictly follow the instrutions in the form/guidelines. Then,  you will be fine. Sometime it takes more than 2 months or so due to lot. MRP is only printed at Nepal eventhough you submit in DC or any Nepal Embassy.