If you are interested in a layman's guide to these issues, check out "Misquoting Jesus" by Bart Ehrman. I found it to be very accesible as a non-scholar of The Bible.
https://en.m.wikipedia.org/wiki/Misquoting_Jesus
I also took a class in college where I had to buy this book:
https://books.google.com/books/about/Gospel_Parallels.html?id=AldMcgAACAAJ&source=kp_book_description
It is educational to see Matthew, Mark, and Luke lined up in parallel so you can easily examine similarities and differences.