Agree that an opera singer/teacher is the best investment you can do for your voice. There is a 10% probability that he/she will try to make a classical singer out of you, and that is something you don't want. On the other hand, there is a 90% probability that a popular singer/teacher will be a waste of time and a serious danger to your voice. There is such an enormous difference in quality, that you will find a whole new world of sound and expression through classical training.

Someone may tell you that the most important part in singing, is the emotional expression, and the sound is a secondary matter. That may be true. There are lots of excellent air blowers who are as expressive as a tuna fish. But when we come to vocal technique, classical singers do know the secrets. And after having acquired the art of singing, you may sing whatever you like.

I would say that a successful plan should not be shorter than one year of weekly lessons, and preferably three years.

Alice has posted many professional and invaluable articles, you may find them by a search of "threads on the singing voice". Lots of luck !

Un abrazo - Andrés (a bass that felt better as a baritone but happened to be a tenor)