mboarder,
The deceased range of motion should be limited to the wrist, if it occurs. Like stated, some patients get significant scarring of the capsule and tissues under the skin, and this can lead to not regaining full ROM, especially at the extremes.
The motion of the fingers should not be affected, unless,...you develop adhesions within the extensor tendon sheaths. Then, of course, you could get decreased ROM. But, usually that can be avoided by being sure to move the fingers right after surgery.
You have been through a major orthopedic surgery, so you know how important it is to start ROM immediately after surgery.
The bone graft is harvested through the same incision, usually on the dorsal (back) aspect of the wrist. It is taken from the distal radius, and just a small amount is needed. So, the surgeon just slips under the muscles, makes a small hole in the cortex (hard outer bone) and scoops out a little of the cancellous (spongy) bone along with a tiny bit of bone marrow. This is then packed into the cyst, after it has been cleaned out. The idea being, that the cancellous bone will both fill in the defect as well as bring in cells to generated new bone.
As to recovery, this is a significant surgery, but not a huge one. Nothing is cut, moved, repaired, reconstructed, etc, so that it would have to be really protected after surgery. It is basically just getting over the trauma of the surgery.
Usually after this type of surgery, the wrist is held still for a week to 10 days for comfort, but the fingers can be moved immediately. Then the wrist is allowed to move to tolerance. You can gradually move and strengthen the wrist and hand.
It takes about 6 weeks usually for the graft to incorporate into the bone, but since this is not for a scaphoid fracture, if it takes longer, that's okay. The scaphoid is still in continuity, so there isn't anything to "protect".
The fact that you do not have any inflammation around the cyst, is good. That usually rules out a tumor or inflammatory conditions. So, it is most likely an intraosseous ganglion or a simple cyst.
You can probably find things on the internet about an intraosseous ganglion. But, basically, it's a ganglion cyst, that has decided to grow into the bone, instead of outward, away from the joint. As it grows, it puts pressure on the bone, gradually pushing the bone out of the way. The theory why they hurt, is the pressure they exert on the bone.
Simple bone cysts usually don't hurt, unless they weaken the bone.
So, depending upon how you do, most patients get back to light activities within 10 days or so. Weight bearing activities (pushups, pull ups, heavy lifting) will take a bit longer, of course. So, if you have a sedentary type job, two weeks and you should be doing most things. But, if you are a manual laborer, then it may be 6 weeks or so before you feel comfortable. You've gone through the ACL rehab, so you sort of know your body and how much you can push things.
Talk to your surgeon for specifics on his/her rehab protocol.
Good luck.