If you're listening to this tape, then my brains are splattered all over a wall somewhere and you've got a job to do.
You need to retrieve the package and get it safely to Ronald Laren in Girdershade. Tell him Grady sent you.
To get the package, you'll need the key. I've stashed it inside an old fire hose case in some maintenance closet in Marigold Metro Station.
The key will unlock the safe that contains the package. Look for the room marked by a spinning light... you can't miss it.
Good luck, and hopefully they won't find you too.