If you want to create  a form  that will pull  data from a SQL backend data
store, I would suggest that you look at InfoPath from Microsoft. Mix this
with SharePoint's forms services and you have a nice solution for your
users. Form Services allows users to fill out an InfoPath form in the
browser, without the need to have InfoPath installed on their workstation.

To answer the first question: yes, you can access SQL data  from Excel
and Word. Those could be in document libraries in SharePoint.
However, if what you really want to do is display a form  which gets
data from a SQL db, then you should go the InfoPath route.

One other view-only option if you don't want to go the InfoPath route is
the Data View/Data form  Web Part. Pretty easy to create  and format in
SharePoint Designer 2007 or FrontPage 2003 (depending on what version of
SharePoint you are running). With 2007 it can be read/write, but it's a
lot trickier to implement, so unless the licensing cost is a major
hurdle I'd go with InfoPath there.