1) Is it as easy as flipping the switch on the back of the PSU and getting some plug adapters?
Depends on the PSU. All the ones I have are auto switching, but the ones with a switch on the back that read 110v or 240v shout work once switched to the 240v side.
2) What is a "safe" amount of juice to pull through a single outlet? Is 10 amps ok? 15?
Depends on what the wiring size, and what the outlet was designed for. I ran a new line for my 240v drop, enough to handle 30 amps.