HAHAHAA WOW they even got her name wrong. Who's "Morimoto?"
Anyway. Re-wrapping the handle is not too terribly hard. Get a couple yards of flat braided cord or twill tape, at least 3/8" wide, and as you unwrap the old one, note how it's twisted and how it overlaps so that you re-wrap it the same way so it looks the same. There may be tutorials floating around online, search for "how to wrap katana handle" or something like that.
Repainting the saya might be tricky, though. It looks like they finish the sword sayas with shellac or lacquer of some kind, so it's not as easy as just slapping a new coat of paint over the top. It might not stick. It might remain tacky, or streak, or go on blotchy, etc. But without knowing what finishing they actually use on these swords, I would hesitate making suggestions about any kind of stripping, repainting, and refinishing method.
Founder and Vice-President, Madison Area Costuming Society, a chapter of the International Costumer's Guild
Strange Land Costuming - www.strangelandcostumes.com