Hi

My 1998 jdm impreza wrx sti has developed a lot of noise from the offside rear wheel, I suspect  bearing failier.

the question is. Is it a fairly simple job to remove the hub and press out the old bearing, and press a new one in ?

     Cheers Steve,

while the bearing is pretty easy remove either with hydraulic press or forcing screw and bearing disc and cup sets getting to that stage can be difficult on older cars due to corrosion of brake fittings and suspension bolts.
The long lateral bolt that goes through hub and outer lateral links is good example of potential grief as they can get really bad (new oem bolt and bush kit is very cheap though).
If your car is pretty rust free or had recent suspension work it likely pretty straight forward, the bearing removal/fitting kits using forcing screw means you can keep hub on the car and save time/money by not needing fully remove hub .
It one of those jobs that pretty easy with good range of equipment and has potential be a complete struggle without .