Definitely do a tour! Although I'm not the biggest...

Definitely do a tour! Although I'm not the biggest opera fan myself and I do not care much about classical music, a tour is really worth it. She is very interesting and with about 45 minutes length very entertaining.
Even better, of course, is the opportunity to see a live performance there. The atmosphere in this historic building alone is worth the money.
The Semperoper is a must when visiting Dresden!