How do I install it?

Simply extract the gamedata folder to your S.T.A.L.K.E.R. directory. Then use a text editor to alter your fsgame.ltx file so that the $game_data$ line looks like this:

$game_data$ = true| true| $fs_root$| gamedata

If you're overwriting an old version, just say yes to any prompts to overwrite any existing files.

How do I uninstall it?

There is no need to back up any of the original files, as they are stored in archived databases in the S.T.A.L.K.E.R. directory. Simply delete the gamedataconfigtexteng folder, and everything will be back to normal.