Is it possible to change the default text font within an open contact? i.e.
the font of the name, email address, tel numbers etc

It uses the same default font as for messages, set in Tools | Options | Mail Format.

Also is it possible to remove the business card from within a contact?

Not without losing some of the functionality on that first contact page; see http://www.outlookcode.com/d/contactform.htm

--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx