I'd say, mostly interchangeable. למידה has a shade of "studying" whereas לימוד carries a taste of "learning", at least to me. למידה stresses the action.
Actually oroginally in למידה the action is the learning and in לימוד the action is the teaching, although nowadays it is all mixed up.
It is right in principle, but as happening with some verbs (especially verbs that have the same word in English for the passer and the receiver, like rent השכרה-שכירה or lend השאלה-שאילה), in which most speakers use the passer word also for the receiver side, it happened also with לימוד-למידה which is teaching-learning.