you could put them into a mesh laundry bag to pre-wash them or a pillow case tied closed- that would keep the tangling-fraying down.
it is a personal choice really - but any fabrics i buy from somewhere other than (new-goods) i would wash ..ie: from thrift stores, yard sales...and yes ebay ect- if they have been in someones-house/barn/garage it would be best to wash them regardless of shrinkage/bleeding thoughts----for safety sake--