Most likely be the problem areas? I just sold my 3.0si Coupe so am familiar with the later N52 ... but if I were to look at a 100k mile 30i E89 aside from things like suspension refresh, anything else to consider?
Roof working ok, corrosion underneath, that's pretty much it apart from the usual with any older cars. No dct, no turbos, no adaptive suspension, it's really not that much different to your E86 mechanically. Best of luck.
As John has said, plus, check the rear lights for water ingress, check rocker cover for oil leaks, if she drives well and has good service history, your good to go.....