And I didn't care for it then either. The hook in the chorus rocks but that's about it. The body of the verses don't make much sense and they rhyme like pros.
She will kill "What Is and What Should Never Be", perfect song for he.
Not sure. The chorus is pretty high (as was Plant's voice) and she gets screechy up there. It's also a very up and down song and the slow parts will be sleepy. The arrangement will have be be very good. There are better Zeppelin songs for her to sing.