I've had two vitrectomies, the last was a couple of weeks ago. My right eye was completely uneventful, the day after they took the bandage off I could see the big E for the first time in weeks! It took a few weeks for everything to settle down, but it wasn't a traumatic experience at all. This was 20 years ago, and I haven't had any problems in that eye since! That is the typical experience, most people recover vision quickly and then are very stable for many, many years.
My left eye a couple of weeks ago I had complications, the trocar (cannula) popped out, so the wound leaked for awhile and it ted to hypotony, low eye pressure, which caused a choroidal detachment. The beginning was scary, because I could see very little and had big black and gray patches. I was taking drops to bring up my eye pressure, and now that my pressure is normalized things are starting to get better. The opthalmologist sounded very optimistic for a complete recovery. Really, long-lasting complications after vitrectomy are very, very rare.
As for the surgery itself, it really wasn't scary at all. Not fun obviously, but not painful, just mild irritation after. They'll probably put you to sleep briefly while they inject the nerve block, so you shouldn't feel that at all. You're awake during the surgery, but it's actually kind of cool, you can see the blood swirling around as they suck it up and your vision starting to clear. I was having a conversation and joking with the doctor throughout (partly because I was loopy from drugs, haha.) I felt drowsy all day, but by the next day felt fine, only had pain when I turned my head quickly.
My sugars during surgery were on the low side, so I set a temp basal and they came back up gradually. (I'd set a temp basal in preparation, but it obviously wasn't low enough.) If you can't bring your bg up they'll put a little Dextrose in your IV...Just make sure to monitor careful because they did that during my first surgery (before I had the pump) and kept it there for much longer than they should have, even though I told them my bg was rising too fast.
Which reminds me of one more thing. You may not have this issue, but my bg's were fluctuating like crazy after the surgery. I finally looked at my Dex graph and saw it was bumping up every 4 hours, which made me realize it was rising after every dose of my prednisone drops. Steroids raise bg, but I didn't realize they would when applied topically! So now I'm bolusing a half unit right after I take the drops, and it seems to be working well at keeping things steady. If you get whacky sugars, look carefully to see if they're happening around when you put in the drops.
Wishing you the best of luck!