Races of Faerûn says that lizardfolk age like humans
Races of Faerûn took the really lazy approach to “unusual” races by just syncing them up with a core race. Lizardfolk get linked with humans, so since reincarnate gives you a young adult body, your body is similar to that of a lizardfolk between 15 years and 35 years old, probably closer to the 15-year-old mark.
As lizardfolk age, they slow down. Over the age of 60 or so, they do not care to do much more than lie on a warm rock and bask in the sun. When thes creatures die, they are consumed by the rest of the tribe at a ceremonial wake, their flesh becoming part of the tribe both literally and figuratively.
By the way, just so it’s clear – your character’s age basically doesn’t matter for much of anything, beyond age category (and reincarnate specifically states you always get a young adult body, so you are almost never in danger of reaching middle age any time soon). Your memories don’t change, so you don’t remember events from earlier than you were originally born or forget events you originally lived through.
Anyway, Races of Faerûn goes on to describe lizardfolk in brief:
They’re primarily patriarchal, with the patriarch basically being the guy who can take on everyone else. Tribes tend to have a shaman who does not lead; presumably their position is a little more stable.
The lizardfolk patron god is Semuanya, though they do not make shrines or hold regular services; the shamans just bring Semuanya’s blessing to their tribes as often as they can. Semuanya is a nature deity, and lizardfolk become druids fairly frequently. Your character, however, would still generally worship whoever he did previously; the reincarnate spell doesn’t change that. See the Special Note Regarding Religion below.
Serpent Kingdoms describes a number of variant lizard-races
Asabis, stingtails, firenewts, khaastas, lizard kings/queens, troglodytes, and trens are all lizard-like humanoids that are described with some detail in this book. Further, the book as a whole is devoted to “scaled ones,” of which the lizardfolk are certainly a member. Thus, it does have quite a few options made for creatures such as yourself.
That said, Serpent Kingdoms is actually one of the most notorious books in 3.5, being the source of the Sarrukh and their Manipulate Form, and thus the linchpin for Pun-pun. The book in general actually has an unusually high concentration of broken or borderline material, even beyond Manipulate Form. I advise your DM to consider its material with care.
But remember: your character doesn’t necessarily know anything about lizardfolk either!
Reincarnate doesn’t change your memories or experiences. If your dwarf didn’t know anything about lizardfolk, well, he’s only going to learn about them as he goes along. Whatever his body’s age is, he doesn’t have memories of more or fewer years than he’d had as a dwarf. He certainly didn’t have his memories of growing up with dwarves replaced by memories of growing up with lizardfolk. And he doesn’t necessarily know how old his lizardfolk body is; after all, he’s probably not overly familiar with lizardfolk biology.
In other words, in a lot of ways, you are really not lacking any information that your character would know. Learning more about lizardfolk as a player may be worthwhile, so you have some idea of what to expect, but ultimately your character wouldn’t have any idea what to expect.
In many ways, explaining this is really your DM’s job
The DM can (and often should) change the world relative to the books, and further needs to arbitrate what knowledge is available in-character. Thus, more than looking things up in a book, it’s often appropriate to ask the DM.
In-character, you “ask the DM what your character knows about the world” by making Knowledge checks. See what your dwarf might have happened to learn about lizardfolk. Assuming you have at least Intelligence 10, you can always take-10 on the Knowledge (local) check (lizardfolk are Humanoids) to learn some basic facts. Your Knowledge (religion) check is probably pretty good, so maybe you can learn about the lizardfolk religion.
Special Note Regarding Religion
But on that note, your faith hasn’t changed: unless your dwarf’s death and resurrection has triggered some crisis of faith, he most likely still worships whomever he previously worshiped. I would guess that most gods wouldn’t have a problem with this; even dwarven gods would probably recognize that he’s still effectively a dwarf in everything but appearance. Thus, you should be able to pray, receive spells, and so on.
If death and resurrection has resulted in a crisis of faith, or your god is particularly racist and narrow-minded, and you’re looking to convert, there are rules for that process. It will involve a quest for the new church and an atonement spell cast by someone of whatever faith you want to switch to.
