Complete pain to get to, front ones not so bad, take the engine cover off, then just follow the leads to the plugs..
Rears..... what a design, actually easier from underneath but still need a bit of witchcraft to do it :angry:
To get the rear plugs out I find it easier to take off the upper intake manifold its called the surge tank, and remove the rear plugs from the top. As they last 100K the same as the timing belts you find it easier to stip the upper intake because it makes changing the belts easier too. The dual platnium plugs looked real good after 100k they probably could have gone another 100k so don't worry about changing them sooner than recommended.
Also it is not really the job for the ambitious amature you need some experience working on complex machinery in confined spaces and get some good quality snapon flexi sockets. The regular tools you buy at the auto parts outlets will not get the job done they are to cumbersome and bulky to get in. BTW plan to set aside a days effort to do the 100k service and have fun.