Transmissions on EVs are generally single stage speed reduction so yes in the extremely rare chance you need to repair it you can. The motors are way harder to repair but they're similarly way less likely to need repair. Other part availability will vary by brand just like with ICE cars/trucks there's nothing magically less available if we're looking at new parts, older common parts there's a bit of a difference just from the designs being newer so there's a smaller population of junked cars to pull random EV pumps off of the way you can with some old car parts.