The counterpart of a repair install in Vista is to do an upgrade of the
existing installation. To do this you run the Vista DVD from the desktop of
the installed Vista OS, not by booting the DVD. Booting only gives you the
option for a custom (clean) install.
Yes it should preserve installed programs and data, however stuff happens so
make sure there is a backup of important data, and you have the original
installation media for all installed apps. I strongly recommend you use
something like Acronis True Image version 10 to image the system before
trying any repairs.
Also try system restore and startup repair, which is accessible by booting
the Vista DVD, before the last resort of an upgrade.
The upgrade process lays down a fresh image of Vista, then brings in
drivers, installed apps and data from the old installation.