Two different questions I see in the OP.
1) Will my current surgeon be offended if I tell him/her I want a 2nd opinion?
Honestly, maybe. It's kind of an ego thing. "I have all this training and experience and you want some fool to second guess me?!" Most of the staff I train under not only accept these requests, they encourage them. Hell, I have one attending who demands a second opinion for every patient that he recommends an elective major surgery (Pediatrics guy, the parents love it). I'm going to actively encourage it myself once I get done with residency. Second opinions, at least intuitively to me, seem like a great way to shield yourself from malpractice suits down the road.
But then again, we're still surgeons, and the ego comes with the package. They might be offended. They probably won't show it. 99.9% will handle in professionally. Seriously, it won't be the first time, no matter who the doc is.
2) Should I ask for a second opinion even if it means risking offending my current doctor (who is just a really nice guy, and kind of cute . . . )
Absolutely. 100%. Go get a second opinion. Do it now. Pay cash for the appointment, it's not that expensive and will probably get you in faster.
At the end of the day, it's your shoulder. Long after your surgeon retires, you've still got that bum shoulder. Long after you get the surgery or don't get the surgery, and he tells you there's nothing else for him to do for you, you've still got that shoulder. Your money, your shoulder, your surgery (or your non-surgery).
The patient-physician relationship is really personal. For you, since you're a nurse (who by definition is supposed to have this whole caring, personal thing going on with the people you take care of) you probably have even more of this going on. But there has to come a point where you step back and remember that it's your body, your cash, your time. If you don't like your care, find another doctor. If you are unsure, go get a second opinion. It's more than just your right, it's your responsibility. Like I said, it'll still be your shoulder . . .
And yeah, find someone from a different group. There are a bunch of reasons for this, not the least of which is that sometimes physicians don't want to offend their partners by disagreeing with them. Also, a lot of groups combine people with different areas of experience and subspecialty training, so it may well be that your first doc is a shoulder-trained 'pod, and his partner you're getting a second opinion from actually mainly does spine . . .