Hi Bill,
Yes you can just reinstall SQL.
To do this, make sure ACT is closed. Open Control Panel and then Add/Remove Programs
Remove the following programs:
Microsoft VSS Write
MXML Parser 6.0
Microsoft SQL Native Client
Microsoft SQL Server Setup Support Files
Microsoft SQL Server 2005
Once they have been removed, insert your cd. Select to Browse the cd, open the Dependancies folder and run the SQLInstall.exe file
Also, as an aside, typically documentation for 2007 applies to 2008 as it is writtend on same basic backbone.