Hello and welcome, Rupert ~
Your anxiety is quite typical for an acoustic neuroma patient facing scheduled surgery and becoming acutely aware of possible negative ramifications. However, although non-invasive (no cutting), radiation, be it GammaKnife, CyberKnife , FSR or some other variation also carries inherent risks. If it didn't, I doubt anyone with an AN under 3 cm would even consider surgery, yet many do. Each approach (surgery, radiation) has it's own distinct drawbacks and advantages, as you know by now. Frankly, as much as I value research (and have done quite a bit) all the AN information in the world won't give you any kind of guarantee of your outcome, no matter what form of treatment you ultimately choose. My usual advice to someone seeking answers is to choose a very skilled surgeon/radiation oncologist with lots of experience dealing with ANs. Know exactly what his (or her) long-range plan is for you and don't ever be shy about asking pertinent questions of any doctor that is going to be working on your skull, be it with surgery or radiation.
Once you've settled on a treatment, doctor/team and facility, you need to 'let go' and put your trust in that doctor and his team. That is easier said than done but most of the folks posting on these forums did just that. I did. Like many, I was rewarded with a great surgery outcome (no complications) and 90 days later, uneventful but successful FSR treatments that seem to have accomplished their goal of destroying my ANs ability to survive. While the tumor is in it's 'death throes', I'm doing just fine, thanks.
I join the many AN patients who, while perhaps not 100% 'unscathed' by major surgery and having radiation beams shot into my skull, did not suffer any real or permanent quality of life issues.
As others have noted, the fact of being diagnosed with an acoustic neuroma and having it addressed, whether by surgery, radiation or both (in my case) is not like having a gallbladder removed or some other simple, straightforward surgery that you undergo, recuperate for a short time then resume your normal activities exactly as you did before the surgery. Every AN post-op patient has some reminders of what he or she went through. I had a splendid outcome but still carry a few very minor deficits that are invisible to others and that I don't allow to impact my enjoyment of life. Like so many, I'm SSD but cope with it fairly well, I think. Other AN post-op patients acquire a BAHA and that basically solves their hearing problem.
As with any other challenge in life, we all approach our individual AN experience, with or without complications, a little bit differently. These forums exist to provide information, advice when requested and support without reservation or judgment as our members deal with their AN issues, including the emotional turmoil you're facing as your surgery date draws closer and the reality of the seriousness of the situation begins to reveal itself to you. All I can add to what others have cogently stated is that many (AN surgical patients) have gone before you, the majority do quite well, post-op and no matter what happens or you decide, we'll be here for you.
Jim