I'm at UAB and took Patho and Role Development together while working full-time. I spent a ton of time studying, but got through the semester and got As in both classes, so it can be done. You just have to really put in the time studying. But as someone else said, you will use all of this information in your career so it is worth the investment. Patho is a very hard class, but you need that deeper level of understand to function at the level of an NP. I still find myself being self-conscious and frustrated in clinicals by how much better the med students understand the processes in the body.
While Patho is hard, it is definitely not the most challenging semester you'll have in school. FNPs are required to know a lot and have a lot of responsibility. I wouldn't worry about how you will function when you get done with school, school will prepare you for that. I think it's just a matter of whether or not you are willing to commit the time it will take to learn what you need to know. It isn't easy, but it will make you into a competent novice NP. Good luck with your decision!