I had to learn this the hard way myself so I'll do my best to help.
If you need to receive the firearm through an FFL holder you will need to have them fax or mail their FFL to the person selling the gun in order for them to be able to legitimately ship a firearm to them.
Most places won't charge over 25 dollars to handle the firearm and do a background check before handing it over to you.
I'm finally getting my C&R to avoid this hassle.. which in all likely hood will be a couple months of waiting. I recommend everyone to do the same.