Your sponsor is responsible for helping you PCS. If you have orders to Iwakuni and your sponsor has not contacted you, contact your gaining command to ensure your sponsor reaches out as soon as possible.
Throughout the checklist and PCS process, you may find it convenient to give your sponsor a Special Power of Attorney (SPOA) so that they can handle many checklist items on your behalf. Coordinate with your sponsor to find the best path forward for your situation.
The sponsor is not responsible financially and should work out electronic payment options to be reimbursed by you (Paypal, Venmo, Zelle, NavyFed, etc.). Your sponsor should keep all receipts and log all expenses paid.