I don't know how helpful I can be, but I can share what I know from my own experiences with these arachnoid cysts.
My son was diagnosed with a very large one when he was an infant. It was an incidental finding and he was monitored heavily through the first three years of life. We did not shunt him or have a finest ration done. We chose to "wait and see". Today he is 9 and seemingly fine. Although, he does have issues with "attention to task" and executive functioning, which make sense, given the location of the cyst.
I had an MRI done about 2 yrs ago because I was hospitalized with meningitis. In a bizarre twist, they told me I had the exact same cyst as my son. Bizarre since this is not a hereditary condition.
Since that time, I have had issues with headaches whenever I am I'll with any sort of virus. Strep throat, cold, flu, etc. any sort of viral illness will bring on massive headaches. I am suffering from them right now, as a matter of fact.
The truth is, most people who have these cysts never even know about them. Most of them are asymptomatic and cause no real issues.
Wait an see what your neurosurgeon recommends and then get some second opinions. From what I read out there, most people who get surgery have nothing but trouble afterwards. That's my opinion, so take it for what it's worth.