I know that many will chime in on this but here are some brief answers, at least from my point of view:
1. Yes, there is a chance of re-growth (or rather that the radiation will not work, so that the AN will not be controlled). There is also a chance of regrowth after surgery. We have seen both types of cases on this forum.
2. The cases of ANs becoming malignant are so few in the literature that they are not even worthwhile mentioning. I think 6 overall, with 3 being after radiation. The risk of secondary malignancy elsewhere may be more important. It is not clear if the risk of developing a malignancy elsewhere in the brain is higher than the general population, but it is always a chance. There is also a chance that something might go wrong with the anesthetic or a serious infection when having surgery. There are risks in everything.
3. Long term hearing loss can happen with radiation treatment (more so with GK rather than CK) and usually over the long term. The chance of facial nerve complications is usually estimated at 2-3%, whereas with surgery it can be as much as 30% or higher, depending on the expertise of the medical team etc - see again reported cases on this forum.
It is true that many doctors mention the age factor. And there is serious merit to this, as very long term data (say over 20 years) are not available for radiation. GK has been around since the 70s, but it was only used in elderly patients, so it was impossible to obtain reliable follow up over long periods of time. The age factor argument may also be reversed, in that many younger patients are dealing with young families, careers etc. and may not be able to afford the long recovery times required after surgery.