Get to the saloon to start the mission. Bentley is now a bartender and you'll need to serve up some drinks to the patrons. Move left and right with the left analog stick (or the directional pad) and press X to throw a drink. When the mini-game starts, you'll need to throw a drink to each one that pops up. After the first few, it starts getting faster and patrons will start asking for more than one drink, so keep an eye on the speech bubble above their head. Once you've served 30 patrons, it'll be time to switch to Sly.
You'll need to sneak by to get to the next area. Use the pipe and the bookshelf to avoid the first spotlight and onto the next platform. Crawl through the hole, then jump past the second spotlight and into the next area. Drop down and go onto the floor, avoiding the guards. See the spinning thing? There's a hook on the one side that you can use to get on top of it, where you'll find a Secret Sly Mask.
Go back to the beginning and crawl through the hole on your right, then use the pipes to get to the upper level. Switch to the Jail costume and hit the base of the pillar with your ball until it gets to the end of the track. Climb and use the ledge and neon lights, watching the lasers in the middle, to get to the other side. All that is left is one last jump from the fan to the vents.
With the RC Car in your control, you will have to watch many obstacles in your way. Besides spiders, there are lasers and fans that blow casino chips that will instantly kill you and make you start over. The path will split, with the left path having fans and the right having spiders (right is easier). The rest of the way isn't too hard, with the mission ending after hearing of Toothpick's plans.