To install, copy the Data folder to your install directory, then add the following text to your archive invalidation file:
Textures/Pipboy3000/pipboyglove01.dds
Textures/Pipboy3000/pipboyarm01.dds
Textures/Pipboy3000/pc/pipboyarm01.dds
Textures/Pipboy3000/pc/english/pipboyarm01.dds
Textures/Pipboy3000/pipboyarm01_n.dds
Textures/Pipboy3000/pc/pipboyarm01_n.dds
Textures/Pipboy3000/pc/english/pipboyarm01_n.dds
Textures/Pipboy3000/pipboyglove01.dds
Textures/Pipboy3000/pipboybtnglow01.dds
Textures/Pipboy3000/screenglare.dds
Also, if you haven't do so already, make sure to change the "bInvalidateOlderFiles=0" line in your "FALLOUT.ini" file to "bInvalidateOlderFiles=1". This file is located in "Documents and Settings\(your user name)\My Documents\My Games\Fallout3" for XP and it should be similar for Vista.
If you don't like the on-screen decal, just remove the "screenglare.dds" file from the Data/Textures/Pipboy3000/ directory and delete the "Textures/Pipboy3000/screenglare.dds" line from your archive invalidation.
To uninstall, remove the above lines of text from your archive invalidation file and delete the corresponding files in your Data/Textures/Pipboy3000 directory.