Hello, and thanks for writing in.
Skin tags are very common in dogs, and rarely result in problems. As with any abnormal skin growth, though, there's a chance they can turn cancerous. The only way to know if cancer is present is to have it biopsied or removed and sent to a pathologist, and they can tell you on a cellular level what exactly is going on. Certainly if it continues to enlarge, becomes painful or bothersome to your dog, starts getting irritated, ulcerated, bleeding, or infected, it needs to be checked out right away. But again, most of these are not cancerous. Of course, if it does bother you quite a bit, you can always request that it be removed, just so it's not there anymore (you would not be the only person to ever do that ;))
I hope this helps. Let me know if I can assist you further.
I would say no, because surgeries are done very commonly on dogs this age. It should especially not be a big problem, since it's considered a minor surgery, he should not be under anesthesia very long, and there should be a quick recovery.