Race change

Hello, i was wondering if i am a Paladin on the horde side(blood elf only) and i want to get a race change what happens then ? Do i need to also change my class or can i play tauren paladin or stuff like that ?

Sorry if it seems like a stupid question but i am curious.

No, it will only show you the available races for your class. And for a horde paladin that would be only blood elf, you'd waste coins/points that way.