You should be able to download the current version of iTunes from here : http://www.apple.com/itunes/download/ - there should be a 'download now' button on the left-hand side of that page.
Deleting the iTunes program shouldn't have affected any of his music or other library content - that is stored in a different place on a computer, deleting or uninstalling iTunes shouldn't touch it. By default the iTunes music and other content is stored under :
- Mac OS X: /Users/username/Music
- Windows XP: \Documents and Settings\username\My Documents\My Music\
- Windows Vista: \Users\username\Music\iTunes
- Windows 7 and Windows 8: \Users\username\My Music\iTunes