It's a long recovery, that is for sure. I didn't have a graft from my hamstring, my doctor used a cadaver (sp) graft so I'm not sure how much extra pain will be added because of the hamstring graft. I never had too much pain before surgery - just a lot of instability. My knee would give out and shift at pretty much anytime. As far as the stability, that does get A LOT better after the surgery. The pain isn't too bad now - sure there are days that my knees just hurt, but it's usually weather related.
Before my surgeries, my doctor told me it was very important to keep my quad muscle as strong as possible, so if I would be driving, I would tighten my quad muscle just to strengthen it a bit more.
Make sure that the day of his surgery and the days following, he takes his pain medicine on time. He wants to stay ahead of the pain - he doesn't want to be without pain medicine.
Feel free to PM me if either of you have questions. I'm more than happy to talk about it especially if it will help a fellow ACL patient.