Can anyone point me in the right direction of how to implement Gun Combat into a 3D Side Scroller. Sorry, Im sort of new to all this.
No need to be sorry 
Epic has a ton of fantastic video tutorials on YouTube. If you want a recommendation, I would say the Twin Stick Shooter would be a great place to get a good head start on the key concepts, then it is just a matter of tweaking the parameters of the game (where the camera and character can and cant go, matching animations respectively). https://youtu.be/1pmPb_TWG-8
Hope that helps!