I would insure it as well, I have seen at least one instance where the USPS insurance paid off, no hassle, and i have heard horror stories about FedEx and UPS on that score.
I also include a printed shipping list, my name and contact info as Seller, name and address of ffl, name and contact info for buyer, and an exact description of what is in the box. I learned the hard way, once shipped a pistol with two extra mags, the transferree was using an ffl he had never dealt with before, he got the pistol and one magazine. What extra magazines? No packing list, my word against the ffl's. I email the shipping list out before hand to all parties, asking for review and correction of any mistaken entry.