1) For someone new to Linux, I suggest either Red Hat or Mandrake (I prefer Red Hat)

2) Yes, almost all Linux distributions are free, so if you get a mainstream one, you'll be fine

3) It's up to you... if you only have one computer, I'd recommend dual booting until you are familiar enought with it to be able to do everything you need on Linux.

4) MS Office will run fine with Wine (a program for Linux). If you don't want to buy it, check out Sun StarOffice 5 (still free for download, thought 6 costs money) or openoffice.org

AJ