Windows-to-Linux. Large Installations Handling the Changeover?

Cathal asks: "Okay. I am a senior in a large Irish university, which is a mostly Microsoft house. As a member of the college computer society, I have heard that the college bean-counters want to reduce the cost of the IT dept. The IT dept are 'thinking' of turning to Linux as a method of cutting costs and improving the service to the staff and the students. I am looking for suggestions and feedback on previous experience in similar situations, (large changeovers, support)." "What the college supports at the moment:

• 9000 Undergrads
• 2500 Postgrads
• 3000 part-time students - night classes
• About 1500 staff and lecturers
• Print farm to support the above, with network printers available in each of the 40 or so computer labs around the place.
• About 25 webservers with a combination of IIS, Apache(win32) and Apache(solaris)
• 300-400 student computers in the on-campus accomodation

College resources:

• About 2500 desktops in the college, at the moment with msoffice on win2k
• A collection of fileservers, and mailservers, (mostly Dell poweredges)
• Fiber backbone, 100Mbit switches, 100Mbit to most desktops, and a 20Mbit connection to net backbone (to go to 125Mbit next year)

If the college does move to Linux, there are a reasonable number of experienced Linux admins as student in the college, running a debian cluster for the compsoc, and could provide a pool of about 10 admins that know the network and the people involved in the running of the college, and could ease the changeover. If anyone has been in a similar situation, what were the pitfalls involved, and the main difficulties in rolling it out? The college *needs* (so I have been told) to have an external contract to solve problems with a defined level of service."