What if any

Training is needed after upgrading workstations from windows 95 to windows 2000? We have in the works to upgrade 75 workstations with multi logins to windows 2000 and office 2000. What am I looking at in user training and trouble shooting! We have already bought replacement hardware for w2k complince and are computer ready for it. But I would like worse case ideas for user training and training befor it is started.