For repairs, yes, you'd have to ship TO FFL.
Shipping FROM an FFL is going to depend on the receiving FFL. Some FFL's will take shipments from private citizens, others will only receive from other FFL's. Best to ask the FFL you're shipping to.
For example:I'm the receiving FFL. I accept shipments from individuals. You get my FFL info, confirm addreess. GO to PO, mail rifle to me. DOne.
Example 2, I'm FFL, I do NOT take shipments from individuals. You confirm address, you go to your local FFL, have him send me rifle.
You're trade partner should be able to help you find out if the receiving FFL will take shipments from individuals. If his FFL won't take from individuals, I'd make him eat the cost of having to pay your FFL to send it.
Hope that helps.