I ran the Providence Marathon in 2016 following a plan from this website:

https://www.halhigdon.com/training-programs/marathon-training/intermediate-1-marathon/#program-list

It provides different schedules based on your ability level and then shows how many weeks to train and how many miles to run on each day of those weeks, gradually increasing your weekly miles. I think I did either intermediate 1 or 2 (I can't remember now), but it allowed me to train well enough to complete my first marathon. There are also other sites with training plans if you search around, but this one seemed straight forward to me.

If you are looking for others to connect with, then I agree with the suggestion by u/brogaant about contacting Rhode Runner. I think they usually have a Wednesday group run and a longer Sunday group run, so you can connect with other runners.

Good luck on your marathon!