congratulations to this wise idea
1) Transfer of Mails
sorry, I do not know this in detail and I think this is tricky in the best case as there are to many different mail clients around filing mails in different ways
2) Transfer of Contacs
Just export it from your Windows PIM Application. Most have the option for some pseudo-standard but all can export it to csv (comma-separated file), which can be imported to your new application, i.e. Thunderbird
3) Transfer of Favorites
They can be exported (normally it is a file named bookmarks.html). With Firefox or Seamonkey you can open this file within the Bookmark-Manager and that is it
4) Overall document
With SOHO your file manager should by default open *.doc *.xls *.pps and other Office Files with the dependant of Linux, normally it will be Open Office. Please check which programs are installed in your system.
Within the file manager you can alway click with right-mouse on an file icon and you get an menu with an entry "open with"
Sorry, with databases I am not so familiar. Open Office can basically manage databases, but if this is an sophisticates customized database you may have a problem. In the worst case you can always try to install Cross-Over from Codeweavers http://www.codeweavers.com/
You might also give Xandros a try as Linux Newbee as this is a Linux distro designed to give as much Windows Look-and-Feel as possible. http://www.ixsoft.de/software/products/XAOC0310CD-DE.html
(I know it is blasphemy to recommend something else than Vector, but for a starter it may be easier to use, so why scaring him away
(runnig Vector 5.8 for work, Xandros for the childs and Windows XP on my wifes machine [guess which colour is her hair