Brian -
first of all I recommend you contact the ANA for their informational literature. It will explain a lot about ANs, your options for treatment, and the possible side-effects of each. They will also send you a WTT (willing to talk) list that will be very helpful.
A tumor your size generally means you have the option of surgery or radiation, and the choice is a personal one based on what you think is best for you. The doctors you consult with will also have their opinions which will help you in making your decision.
Swelling is common with radiation, but in the end the majority of ANs stop growing and die (aka necrosis). Sometimes the AN doesn't stop growing and die and in that case you'd typically have to have surgery to remove it. There are other side-effects associated with radiation, just as there are side-effects of surgery.
I had surgery, and while you are right, you don't know what might happen it's a very good option for some. It was for me. My only permanent side-effect is SSD (single-sided deafness) and it sounds like you've already got that issue. My SSD has been helped tremendously by a BAHA; there are other options available.
You need to educate yourself on both types of treatment and then make your decision. Make sure you consult with doctors who do both surgery and radiation - some do both, some don't - but basically you want a well-rounded medical opinion. We can give you our thoughts on what you should do, but in the end it's your choice. We'll support you regardless.
Jan