1) If I rollback to a Restore Point prior to a problem (about 2 1/2 weeks ago), what will happen
to any s/w added after that restore Point (e.g. Windows updates/patches, MS
Office SP3, 3rd party software)?

It depends; when you go back to a restore point, you go back to versions of the registry and some other system files which existed at that time.  Hence, some installations may have to be re-installed because they are no longer properly "registered" in XP, in the Registry in particular.  Others will continue to work fine.  Go to Windows Update and check to be certain, and do a similar check for Office.

 

2) If I use the "repair" option on Win XP CD, will this function overwrite
any Windows s/w that may have been subesquently updated via patches?

Yes; the Repair function restores the system to the way it was installed except for the Registry and a few other files.  You will have to re-install all updates to Windows (Windows Update will list them for you).  I do not know whether that will be true of Office.