If you can plug in a lamp and have mastered "left loosey, righty tighty" you can change your own plugs. It may take a couple hours the first time, but it really doesn't require any special knowledge or any tools beyond basic hand tools.
You need a basic socket set, simple bar style torque wrench, spark plug socket, spark plug gapper, a 4" extension, a 6" extension, a wobble joint, and a long extension, 10", 12" whatever. A stubby 10mm wrench will also make life easier.
Pull the spark plug boot off by hand. Put the spark plug socket on the short extension (either 4 or 6, depending on how much room at that cylinder) and turn left until the plug comes out. Gapping a plug is as simple as bending the little wire until the correct size feeler goes into the gap. Gap the plug, put it in the hole, turn until it feels tight, then put the torque wrench on it and push until the little needle points to the 14 on the ft/lb side. Use the 10 mm wrench and 10mm socket, remove the coil pack next to the spark plug boot, (2 bolts, one top and one bottom) lift it up, do the same thing under there to remove and replace the spark plug. Put the plug boot and coil pack back on, move to next cylinder.
The only remotely challenging thing is getting to the front 2 cylinders on the driver's side, and that's where the really short extension and wobble joint come in. Drop the short extension and socket in the hole, plug in the wobble and a long extension, and you're turning the wrench way above the tight mess.
You'll save yourself almost $300 and it really is that simple.