My husband has had this done in both of his eyes..
I start witht the worse one first of his operations
The first vitrectomy was carried out 10 years ago, after he had a major hemorrage in his left eye, the bleed caused instant sight loss (couldn't see through the blood) but it also detached part of his retina, so the operations involved removing the blood clot, reattaching the retina, the vitreious jelly is removed as part of the operation and replaced with a (in my husband case) a gas bubble to keep everything in place while new vitreios jelly is forming...
The actually operation took about 4 hours, and after this he had to do what they called 'posturering' where he had to lie in cetain position to ensure everything settled correctly, the out come of the operations was a complete success and he has no futher problems with that eye, but with saying that the is one guarantee that they do give, after the operation because they've cut the eye to operate you will at some point of the future have to have the cataract removed and replaced, which they can't say when this will happen, for my husband he's just been told that they are going to do this soon...
His right eye was operated on about 6 years ago and a lot less complex and sounds at though it's very similar cercumstances to yours, he had several laser treatments to this eye, and then they dicided to operate to stablize it, this was very straight forward with a lot less time in surgery and required no prosturering procedure after... It was explained at the time that the intention was to stablized the eye to prevent any futher damage to it, not a operation to improve the sight in that eye.. My husband was one of the lucky ones as the operation did improve his sight, so he and the surgeon was chuffed with this out come...
Since having these operations he hasn't had any further bleeds or required any lasering of either eye, the cataract that he's due to have done shorty due to his first operation and something that we had been warned at the time would adventually be needed...