Bulk Category Switching

Hi, working on a big blog: http://blog.sportsbetting.com and they have requested to change and clean the categories to make them simpler ones. I have found two issues:

1- Cannot change the categories in bulk
2- Have had trouble including category names (i.e. Football Betting I wanted to change it to NFL Betting, went in and changed the name, nothing happened. So I decided to go and create a new category NFL Betting and move all the posts to that new category but now it says that the category already exists)

Any help would be highly appreciated.

Ricky