Casinogirl68 is the expert, but I think I can handle these questions, since I've played in almost every one of their events...
You noticed the $25K added. That's been a constant in every tournament. It's always been $25K regardless of number of players.
This is a funny money event, and the structure is unusual. The first two rounds are non-elimination, or accumulative style. You'll be given $1000 in each round, and your total score at the end of the round will be noted. Your score for the first day is the sum of your two rounds. The scores are ranked, and the top 35 players advance into the semifinals. Semifinalists are guaranteed $500 in prize money, so at that point it's a freeroll.
The unfortunate soul in spot 36 gets a consolation prize, his $500 back, though he doesn't get to play in the semifinals. There are drawings into the semifinals, and into the finals.
Once you reach the semifinals, the tournament reverts to the traditional table-advance style. You'll be competing against only your table, with one player advancing into the finals.
This tournament format is obviously convenient for the casino, because they can accomodate a large number of players without having to change the structure at all. Some players hate accumulative rounds, and I can sympathize. I don't enjoy those rounds nearly as much, but I do believe that I have a large advantage in those events, because many players just don't bet aggressively enough to give themselves a chance to advance.
Of course, many players think I bet TOO aggressively. If you've seen me play at Bally's you might agree! One of my favorite stories from that tournament is when I went all-in on hand one (as usual), and drew a pair of Aces. Being unable to split, I hit twice, and busted with two face cards. There went my two 21s!
It's no secret that I'm a big fan of this tournament, although I've never made the finals. Bally's does an outstanding job of running it, and believe me, they've had a few interesting situations they've had to handle over the years. They get an A+ from me every time.
Also, they do a great job of spreading the wealth. If you make the final table, you'll win a lot of money. Unlike some events that are way top-heavy, look at this payout from the event earlier this year:
$65K / $25K / $18K / $14K / $9K / $7K / $5K