hi Pete I'm a mechanic by trade, I don't specialise in Lexus but know my way around them, I take on all makes of car.
Are you doing both coils? there's no trick really, the one on the bank near the airbox is quite easy to get to once you remove the air box and engine cover. the one near the battery is a little fiddly, you will need the engine cover, battery, air box removed to get a good look at it. on each coil the wiring loom is a little short so it's tight access to get your fingers on the plugs. a 10mm socket on a 1/4 ratchet and you'll be fine, just try not to drop the bolts!