Not had the op (just a bit of patella tidying last year) but there are plenty of posts in the cartilage repair section http://www.kneeguru.co.uk/KNEEtalk/index.php?board=35.0
(and maybe the patello-femoral section)
and also some post op diaries...look for posts by cdubb, she had patella ACI with a TTT I think and also someone called thabo (among others)
Are you having any sort of realignment at the same time - to address any tracking issues that have caused the damage?
Good luck, it's a pretty big op. Make sure you ask your surgeon lots of questions and get a good physio sorted. As with any knee surgery, getting the muscles as strong as possible beforehand is very important