Greetings

Just started playing last night and haven't exactly gotten much around, however I'm currently on the task of Killing a "Kyle Barnes" and I did find him along with his body guards.
Now only problem is that the body guards and Kyle himself respawns shortly after killing them so I dunno if I'm just supposed to leave the 'shooting gallery' once I've killed Kyle and X amount of Body guards??

Oh and if any of y'all would be kind enough to tell me what I should be doing as a Spy/Assassin? Jack up rifle skill or should I spend my points towards something else perhaps?
Where should I go to get a better gun and Ammo?

Thanks in advance.

- X41823T