how do i replace door handle

Remove the door panel for either inner or outer handles. Get a flashlight and find the bolts or screws inside the door for the outer handle and remove them. Unhook the linkage, might have to swap the door lock tumblers if its a front door. If its an inner handle unhook the linkage and unbolt or unscrew it from either the door itself or the door panel. It's pretty easy to do if you're mechanically inclined. Just go slow and try not to break any of the door panel clips

any tips on on getting the panels internal handles and armrest off also; don't quite get the tumbler swap thing

I've never worked on a Starlet before however door panel removal is pretty much the same no matter what kind of vehicle it is. Look for holes underneath the armrest or a cover that will snap off to expose the mounting screws or bolts. What year is your starlet? Which handle are you replacing, inner or outer?

1997 outer right door

Can you post a picture of the door panel? I can walk you through it.