Rachel is not looking forward to "tomorrow", because she is planning to return Barry's engagement ring, which will be hard to do without the ring.Oh, like I wasn't dreading tomorrow enough, having to give it back to him
Apparently, she left him standing at the altar. (Talk about last minute!)I'm the girl in the veil who stomped on your heart in front of your entire family!'
"Doy!" is an exclamation, and as such it doesn't really mean anything all by itself. (It is, I think, quite similar to duh.) Phoebe seems to think that Joey should know the answer to the question.
Does that help?