Not sure if it's the info you are looking for but bmw sells the kit with all the buttons except the centers of the 2 knobs. Did mine after I bought my e90, can't remember the price 100% but I think it was between R500 and R700.
It's pretty simple to do aswell. Unit just clips apart, new buttons clip in, easy peasy, I don't recall any screws but there may be one or 2 torx screws. Hope it helps