Looking for advice taking it to the next level

I would call myself (31M) a part-time runner. I usually sign up for one race a year to push myself to run and get in better shape, train hard for a few months leading up to the event, then as soon as I finish I don't run any more. I do stay active in other ways.

I have signed up for my second marathon for October 2025. In May 2024 I ran my first marathon and finished 3:53:11. I basically winged it (wung it?) training wise. I trained for 12 weeks, running 5x per week, peaking around 75km/week. Training was definitely a grind, but I lucked out with no injuries and being able to stay consistent and exceeded my finish time goals/expectations. I didn't really change my diet much, nor did I do proper recovery (things like stretching, foam rolling, icing, etc).

This year I want to do dig in and try to push myself further. I found a Pfitz 18/55 training template that I was planning to use for the actual running side of things. I am disciplined enough to do the actual running consistently, but I'm looking for guidance on the nutrition, recovery, and other factors I might not even know about to see what I can do with a proper regiment.

Any advice on where to start? I have health benefits I've never looked into like coverages for dieticians, athletic therapists, etc that I don't know if it would really help or not. Any insight would be appreciated! I work well when I'm given a plan to stick to, but I'm struggling with coming up with that plan myself.

Thanks in advance!