The library's a better bet than wikipedia. Although it'll probably require more patience. Everyone and their aunt Ethel can edit wikipedia, so there's no real guarantee that it's accurate. Or the sources people have taken the information from are accurate....
Also; I think some of your questions aren't helpful, and won't get useful answers - especially "how many troops can a war galley carry", as there are so many variables, not to mention there's not really a standard size for them, or indeed most of the old ships. They might be able to carry more troops over a short journey where fewer supplies are needed, they might only be able to carry a boarding party, they might have rowers, they might be sail powered...
"What sort of damage could a merchant ship sustain..." Well, if we're talking degree of damage, then, again, what size, how is it rigged, what type of hull, how many crew, any rowers? If we're talking what type of damage, then hull, loss of crew/rowers and sail. A leaking hull will take on water, adding weight, slowing it down, etc, and might even add to the drag the ship suffers. Loss of crew or rowers (okay, or oars) and obviously things just don't get done as fast. Lost and damaged sails mean less wind effect.