Personally, I would try to sell locally first -- benefit your community. Selling by the yard would require that you either measure each piece in advance and mark it, or measure each piece as you sell it... a lot of time and effort. Seems like by the pound makes sense. Would suggest that whatever you have left goes to the local guild for projects (you already belong more than likely) or donate to Goodwill, church group etc., that once out of your stash, never to return to the collection! Then you can enjoy the use the fabrics you have kept, and others will enjoy their new fabrics.
If you decide to sell on any online site, it will require posting, managing, replying, waiting for transactions to occur, packaging, mailing etc. etc. Your time involvement would be quite extensive.