Talk to the Admin and they might give you special exception as a bereavment sale, you've a few choices othrwise, FB and are a flat no for guns even though allows it in other countries, parts can sometimes be allowed though dependant on what they are.
Web wise theres Guntrader, Gunstar and Guns and gear off the top of my head, basically a bit like a classifieds section in a newspaper, just say what you know with as many photos as you can and jobs a good 'un, obviously theres many forums but like this one they can have requirements to sell so speaking with their admin teams would be the only real way.
Lastly it's just searching out an RFD in your area, you wont get as much as a private sale but it does remove some of the hassle.
Sorry for your loss and good luck.
You'll Shoot your eye out Kid