Remember - IF HeyGal catches you processing gun parts, they can suspend your account. If you do choose to go that route, I wouldnt advertise it in your auction (just offer it after the fact), and make sure that the buyer doesn't make any references to guns when he sends payment. Since I NEED my HeyGal account for ebay, I just take checks/money orders on gun broker, and make it clear there will be a wait time for it to clear.
When making your listing, browse through a few similar listings and figure out what rules folks are applying to listings of that type. What states people won't ship ammo to, things like that. And put clear auction terms at the end - return policy, shipping policy, payment type and time frame policy, things like that. Browse through other auctions and you'll get an idea.
Finally, nobody likes reading a block of text, so you're not geeky inclined, you can use an online HTML editor like this one to get something passable looking. Or at the very least, remember that you can break to the next line of text (ENTER key) with <BR> at the end
http://htmleditor.in/index.html
Here is an example of how I format my auctions:
http://www.gunbroker.com/Auction/Vie...Item=328574372
(oh yeah, and CLEAR photos are an absolute must and go a long way towards hooking buyers and convincing em that YOUR product is the one they want and not the other 10 identical ones for sale)