Thanks Norbie. Yeah the driven gear is easy to get out (pulled it out to count the teeth) - don't see how it would be possible to change the other one without dropping the tranny.
There must be someone out there who knows if what I would like to do will work? Anyone work for Toyota? If not I guess I'll have to take a punt & blow $60 on a 35 tooth gear which may end up as a heap of plastic shavings in my tranny!