It is common to be scared and overwhelmed too. Sorry for your husbands diagnoses, it's tough being a caregiver and having to watch someone go through the treatments and not be able to do much. I had to take care of my Mom and Dad both when they fought cancer, as well as being a 3 time survivor myself.
As far as a second opinion, you will get lot's of opinions about that. Most of the time they never hurt. My question first is, why do you think you need one? Do you not trust the opinion of your oncologist? Are you doubting what they have told you, are you uncompfortable with them?
Give a little more detail and there are great people here that will give some thoughts on it.
Thanks for posting, I hope the Mr' is doing well.