mazda 323 1998?

This is not a job for an amateur.

But you asked:
I will assume you have some knowledge of front wheel drive cars and some basic knowledge of how to do things

jack up and remove front wheel.
Remove calliper and support.(dont hang on hose)
Remove front disc.
Remove front hub nut. (best of luck)
Undo bottom ball joint nut and disconnect hub assemly from lower arm (hit the joint REALLY hard with a big hammer and then lever hard - dont hit the cv joint or boot).
Remove the nuts from the top of the suspension strut in the engine bay but NOT the middle one.
Support suspension leg, remove the big circlip.
Place a drift into the middle of the hub and smash the bearing out.
Cut bearing shell off of hub without damaging the hub(use a grinder and watch for the blue colouration of the metal then hit with cold chisel to crack it)
Drive shell out of the leg.
Borrow 15ton+ bearing press.
Press bearing into suspension leg
Press hub into bearing.
Replace circlip.
Reassemble your car.

Again if you don't know what your up to dont try this, there are so many ways to go wrong and really hurt yourself. Take it to a garage.

Dave the wrench.
January 2009