1. i check which mods are a "MUST HAVE". If i remove the gallery in an photographer/event forum, i'm sure that i'll lose 3/4 of my users, even i would bring some months later another gallery back...
2. check if importers are available for the "must have data". Back to the photographer forum: i'm sure most would hate me and stop supporting the page, if i would delete all the photos they uploaded in the last years.
3. I'm altering the style of the NEW FORUM to be similar to the old forum.
I think that most of "average joe" users don't want too many changes and because they need to learn how the new software is working, they shouldn't bother also about a completely changed design.
4.After the conversation I disable many features and activate and introduce them weekly.