In regards to sleeping bags, most people bring them because it's small and light, so they are easy to carry. Basically, you guys get given an empty bed, so it's up to you how you want to sleep. You'll need something to put your head on (so pillow, clothes, etc) and something to put over yourself (so sleeping bag, sheets, etc). Up to you guys.
The meeting place is behind UTS Building 5 at the Haymarket Campus (as shown on your map). You'll see giant bus bays there, so just wait there. It's about a 10 minute walk from Central. Take the intercity exit (the one facing George St, not Eddy Ave) and go down the hill and cross at Railway Square. Then go down Quay St, turn left at Ultimo Rd (when you see the UTS Library) then turn right into Darling Drive. Alternatively, exit Central station on the UTS tunnel side, go all the way through the tunnel, go down behind the ABC building, down the ramp all the way to Ultimo Rd and then just then left onto Darling Drive. If that's all confusing, then just find your own way to get there and leave yourself with plenty of time!