I think the only issue for some people will be matching the wires due to them being a bit different in colors. Although I know the ground wire is almost always the same color.The OEM fog light kit plugs into existing harness already in the car. It's already wired in weather the car came with or without the lights. I would assume you can use the same method to install any light, OEM or not. Look at another post where a member included installation manual for the factory kit.
The rule of thumb it to fuse the new circuit with a smaller fuse than the circuit you are taping into. That is one way to avoid damage to existing parts. It is also wise to let someone more experienced do the job if you are not sure of what you are doing. Most dealers will install aftermarket OEM parts without any fuss. That is more costly but it insures there are no problems down the road.What would happen if you accidentally wired something wrong? Would a fuse blow or something, causing permanent damage?