This is a story related achievement / quest.
This achievement is tied directly to the quest X-8: high School Horror!. Here is a quick run through:
Travel to the X-8 research center.
Begin the residential cyberdog guard test at the X-8 test terminal. This test requires you to collect three sets of data from the facility. The way in which you are to collect them is the test itself.
Continue to search through the facility while looking for Gabe's digging sites and trying to find the Audio Sample - Gabriel's Bark..
When Gabe dies DO NOT attempt to loot is body right away. He will blow up after 10 seconds and will have the blast radius of a mini-nuke going off. It is best to simply hide and take cover and return after the explosion. It's also noteworthy that Gabe can in fact be saved, but you need to be quick.
After you retrieve the audio sample you will have completed the quest!
While some of the monsters and bosses in this DLC do require skill, strength, and high quality weapons, with a high amount of sneak a lot of sneaking around can be achieved. Also remember that you do not have to go everywhere, complete everything, and hoard as much as you can in one trip because you can return to Old World Blues whenever you choose. Some of the monsters are pretty tough and the situations you are put into require fairly high science, medicine, barter and lockpicking. With a little bit of planning, and effective use of the links to better diagnose the places you are going into, you should have no problem conquering this exciting DLC. Best of luck.