Search online for a stereo installation guide.
Or do an advanced search here in the audio/visual section.
Or try searching over at the
VVTI.NET Audio section They have a lot more people there with your type of car than here
Or you could do like me the first time I did one and just start taking shit apart. Eventually you will get the old one out. Then you have to plug in your new wiring harness.
Basically any decent HU should come with good install instructions and a wiring harness, so it's mostly a matter of getting out the old one.
Hope this helps