you can draw out an ellipse/ circle with the path tool, but chances are you wont be able to make it exact.
IMO, the best way to put text onto curves / shapes, is to do the text in illustrator, then import it in.
you can make the text .eps / create outlines so you dont encounter any font problems. if creting text to outlines, keep 2 ill. files, one as .ai, and the outline version as .eps, that way you can still amend the text if you need to