Soo I was about 15% through my novel and I realized...I really want to write the novel with a split POV. The majority will be through the main character's eyes, in third person, whereas I'd like to insert a second POV in diary/journal format ("I said, I liked...etc."). Is this too disconcerting? Should I stick to third-person through the whole novel? Any feedback is welcome!
You can have journal entries as block quotes. If you do that, you can either show the character making the entry, or you could use a journal entry at the head oif each chapter. Neither of these would really be a POV switch, but could serve your needs. I wouldn't recommend doing a real narrative shift to first person in the narrative body. The difference in the "feel" of first vs third person doesn't make for smooth transitions.