Eajr,, once you can post it for sale,, and a buyer is found,, it's not too hard to handle the transaction.
A lot depends upon how & who you use to ship the gun,, unless you do a local sale. The absolute best & easiest way is to find a local FFL (to you) that uses the USPS shipping method. It's MUCH cheaper than FedEx or UPS. A handgun, shipped USPS with insurance is around $20.00. If you are good friends with the FFL,, he'll only charge you a nominal fee (usually about $10-$30) to enter it in his books, package it & ship it (insured) to THE BUYER'S FFL! It can only go to a FFL of the buyer's choice. And the buyer's FFL will be required to send a copy of their FFL to the shipping FFL. The buyer can send the payment to you in a form you'll accept. Once you receive the payment,, you ship the gun.
Sadly,, many FFL dealers charge a LOT more than they should for this type of simple service. And some only use FedEx or UPS. If you find that type of FFL,, keep looking. I have told a few FFL holders that due to that type of attitude I won't be shopping with them or supporting their business. For a FFL dealer,, the total time involved to enter in the book, and later out of the book, and package & ship a handgun should be worth an hour's time. What is a fair hour's time or work? FFL's who say they only do it for $100 or more make the cost of the firearm go up,, and that can hurt a potential sale.
And for you as the seller,, need to look at the total cost to the buyer when you price a handgun. The buyer's do,, so price accordingly. That's why using a FFL dealer who is a GOOD one,, and who doesn't do things to make the expense of shipping go way up is the best way to go.
So my advise is for you to find a good FFL dealer, let them handle the legal paperwork, and you won't break any laws, AND it'll go a lot smoother.