sorry but someone just helped me evolve it. to answer your question, yes the pokemon evolves after you get it in a trade, if thats the way it evolves. after you get the poke it will say haunter is evolving and so on.
anyways thanks for replying and offering to help =)
Quick question: I've never traded where the pokemon evolves once it's traded.. Does the pokemon evolve the moment I get it, or do I have to leave the wifi for it to evolve?