The above issues are just a sample of the issues you need to consider before you start to order the new PC's and printers. All those parties involved in the implementation must be consulted at the outset, including third party support for specialised software, and at least one person should be appointed to co-ordinate the whole project.
Above all, do not leave the organisation of the training until everything else has been decided. The training is going to be the key to your successful implementation.
Timetable for Implementation