You need to change the following two perceptions.
1- "But, I know engineering is going to be difficult" What makes you believe this perception? - We all come to this earth not knowing a thing.
2- "I still want to do it, but I worry if the level of studies are out of my league." - We are all in the student league.
You are right in meeting the prerequisites: "I still have the core classes to finish"- You need about 124 credits +/- to graduate. Everyone does, not just you.
"Is it too late and too difficult for me to succeed?" - If you do nightly homework, have good attendance, it is average effort. If you are breathing today, it is not too late to start.
Once you change your perception that engineering is not hard, that it is learnable and that you can do this you have a great start.
Once you go on to fulfill the prerequiste classes, you would have enough credits to graduate.
On a related topic- Once I heard a professor mention that most of the students who fail Calculus I, had a negative outlook prior to taking this class.
Change your perception, put in some effort and leave the world without any regrets.