Most Scions have a black plastic shield over the top of the engine you remove, then disconnect the electrical connection at each of the ignition coils that sit above the spark plugs,the coils are usually secure to the valve cover with a 10mm head bolt, you need a 3/8 drive long extension and ratchet and a 5/8 spark plug socket to remove the plugs.
There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
I just replaced plugs on a 2008 xd. they DO NOT take a 5/8 socket. A LONG EXTENSION WILL NOT WORK. I used a short extension connected to a 14 mm socket. I attached a universal between the ratchet and extension. this allows you to snake it in the limited space between the valve cover and the cowl. I unscrewed the plug and used an extendable magnet to remove plug. I also used a flexible claw parts grabber to place the new plug back in. I had just picked up the magnet and parts grabber at lowes for $3.99. worked great. I'm sure you could buy a 14mm plug socket. had 40,000 miles on denso iridium plugs that were still working ok. sorta expensive, but cant argue with the quality. also only had to disconnect the connector on the far right hand plug. it says rookie, but I don't answer things I'm not certain of.