If you saved your Stealth Boy from the Goodsprings Schoolhouse, ignore that video's recommendation. Getting to the clinic is trivial with JIP Fast Travel Anywhere otherwise, take this route. You should also rush the Intelligence implant at Level 1 because of Politician's skill penalties. If you're going for a Pacifist run (with STUN, for example), steal 50 NCR Dogtags and trade them in for rep at Cottonwood Cove.
The key will be given to you about Lucius at The Fort, northeast of Boulder City, but you must be Liked by the Legion.
To get the Lucky Shades, you need to gain access to Caesar's Legion's safehouse, southeast of Nipton. With the Small Frame trait, you can buy one less implant or choose one less Intense Training perk (better option) to max out Agility. Luck: 7 (Implant +1, Dead Money +1, Lucky Shades +1).Agility: 4/5 (Implant +1, Intense Training +4/5).Charisma: 4 (Implant +1, Intense Training +5).Perception: 6 (Implant +1, Lucky Shades with Four Eyes +3).