score:4
Aside from a few hungry all-night clubbers and the odd loaded sushi fanatic rolling up in a cab, everybody else will be in the same boat as you, so you're quite likely to get in if you arrive on the first train.
Also, while for some reason the auctions get all the press, the main event at Tsukiji is actually eating the world's best sushi. I'm pretty sure you won't regret if you skip the auction entirely and go eat at Sushidai or Yamato Sushi instead. Turning up early for these is a good idea as well, they're tiny and the queue to get in can be 1 hr plus if you get there late.