Could scar tissue from my appendectomy make it more difficult to have a c-section?

It's possible. Any previous surgery can complicate your future surgery. After surgery, adhesions form within days of surgery on the inside of your body. During your next surgery or c-section, the surgeon may encounter these adhesions and depending on how extensive they are, the surgery could become complicated and longer. This is usually due to distorted anatomy and scar tissue.
Only if complicated. Rarely will the appendectomy scar cause a problem with a c-section scar when the former is a mcburney type incision (#3 in picture and the most common) and the lattter is a pfannenstiel incision (#9 in picutre and most common). In rare instances of rupture and abscess and wound dehiscence interference could be possible but unlikely.
Rarely. If you had a ruptured appendix that can sometimes cause more scar tissue.