Hi Tim,
It depends on the size of your collection, whether there are any niche or rare guns, and how quickly you want to get rid of them.
Do you have any ideas of current values? If not, you can by all means ask for valuations on here, but you need to be accurate with descriptions and be prepared to take lots of photos.
A dealer is a quick and fairly reduced hassle option, but remember you won't get the best price as they rightly have to make their margin. They may also miss a rare gun/edition that may get recognised here.
Start with a list on here and see what kind of interest you get. Also search previous posts to see if they give an idea of values.
Not everyone wants to, but be prepared to post a well packed gun by Parcel Force so you don't limit your buyers.
Good luck...
Ash