I'll try to answer as many of your questions as I'm able:
The avn.com usually has a list of the stars appearing. As it gets closer to the convention, that list gets more accurate but there's always a chance that someone won't show up. There's also a chance that someone will show up that is not on that list. Many times, the ladies are not paying their own way to these conventions - their expenses are covered by a studio, or other company that wants that star to represent them. So, sometimes, one star may get substituted for another star, or a deal might fall through, or one of any number of other things can happen. I'd say the list for these conventions is probably about 90% accurate though.
To find out which of them are providers is not hard for those that are not UTR: search here, search on your favorite agency's website, search the Internet, etc. The UTRs are harder. BTW, last I checked, Jenna Haze does not provide and likely never will. That opinion comes from my conversations with her, as well as conversations with her that have been relayed to me.
Since AVN is in Vegas, you can also check with the various brothels in Nevada including Denis Hof's two locations for The Bunny Ranch and The Love Ranch. The Love Ranch is just outside Vegas - far enough to be legal (prostitution is not legal in Vegas so be careful).
As for how much cash to bring: you might just need to bring whatever you need for day to day expenses. You may not need more than that. Here's a little trick that I used in Atlantic City and Reno - I imagine it works in Vegas too: you take your credit card down to a casino, do a cash withdrawal on the card and they give you chips. Casinos are used to this and it's quite common. You spend an hour or so gaming (don't lose too much) and then you go cash out and turn in the chips you have left. Voila! You have cash.

Yes, it probably costs a bit more because most cards charge a fee and/or interest for cash withdrawals on the card, and you have to make sure you withdraw enough to cover whatever losses you might have in the casino but, it sure as heck beats having to explain to a TSA officer why you have $10K in cash, or risk losing your money to a thief along the way. You can't do this trick too often - maybe once or twice a week. More than that and someone might get suspicious. It also helps if you don't have a limit on your credit card for cash withdrawals.
There are probably other options. For example, one of the things I used to do when traveling in Europe was to take my American Express card down to the American Express office and withdraw cash directly on the card. I don't know if there's an American Express office in Vegas, though or where. You might also check to see if your bank has a branch in Vegas or nearby - it might be easier to just take a taxi out to your bank and withdraw cash that way. It depends on your bank.
If you're dealing with the brothels, it's even easier. I think they take credit cards. At least The Bunny Ranch did - don't know if they still do or if The Love Ranch is set up the same way. Denis has about 20 or so porn stars that he can book but you have to go to the ranch in person to do it. Both have web sites so you can go there for more information and see who you can book.
If you're dealing with an agency like TLC, give them a call and find out what they suggest. I'm sure this has come up in the past and they might already have a solution. They might be willing to accept a wire transfer or something like that which is fairly easy to do if your bank has online banking and you're set up for it.
Hope at least some of this helps.