I'm still having some problems negotiating this website,...somewhat strange (at least to me).

So I was trying to recall if selling was allowed on this site?? (I have about 50 O-scale, 2-rail cars that I am not going to use)

Sorry that you are still having problems. As always, all you have to do is ask.

The Swap Meet is what you are looking for:
https://bigbluetrains.com/forumdisplay.php?fid=5

Best of luck!