The original question was: Is it possible to breach the center of a nebula? All the gases around it would make it hard for us to achieve this correct?
Physicist: It wouldn’t be too bad. If you were in a nebula, you probably wouldn’t notice the gas at all. The difference between deep space and the inside of a nebula is pretty small. The fact that we can even see nebulae at all is due to the fact that when we look at them, we’re looking through several light years of dust and gas, which adds up. If you were actually there, by the time the gas was dense enough that you’d notice it at all, it would already be in the process of collapsing and you’d find yourself inside a new star in short order.
Nebulae are in general huge. So getting to the middle of one in any reasonable amount of time would involve moving at relativistic velocities (near light speed). For example, the Orion Nebula is about 24 light years across. To get from the edge to the center in less than several years would require moving at around 95% of light speed or faster. But at speeds like that even small pieces of grit (common in planetary nebulae especially) become very dangerous.
So, yes, you can definitely get to the middle of a nebula. But you either need to take your time, or have a fast, well armored ship.