oh lawdthe tranq sniper rifle isn't going to help you if doesn't have a suppressor. i personally like to recon areas before the mission. there's a side entrance in the honey bee mission that can lead you to the target faster. i found it by exploring in the area in free roam. if you study the map you'll notice most of the locations will have side and back entrances.
btw: you get the ability to customize weapons, which means you can put all sorts of attachments on weapons, it's