Paleontology and evolutionary history are subjects fraught with that particular peril, agreed. I took a quick poke and found
a fairly concise site that addresses a lot of the possible questions with decent clarity, though. Worth a few minutes of reading if it isn't too far below your existing knowledge level.
All true, and worth noting that even large sauropods don't seem to have ever developed the mammalian multiple-stomach trait. Some (possibly many - that seems to be unsure as yet) of them did have discrete gizzards like birds do, which is discussed at the link above, and gastroliths (another digestive aid used by many avians) were commonplace in all manner of herbivorous dinosaurs - with the big browsers having an impressive number of them in their large single stomach. Also worth noting that the treetop and water-plant browsers were chowing down on more efficient foodstuffs than grazers, so they evolved differently to reflect that.
But that site explains it all better than I can without getting overly deep for casual reading.