Congratulations!!
Your hard work and dedication paid off. From the sounds of it you have just scratched the surface of your fitness potential. So keep at it.
As for a running plan. If you are new to running training bear in mind that the Luke Nelson Intro to Ultra plan recommends that you are able to handle back to back 25 miles/wk. If you are not at that level you might consider the beginner marathon plan just to allow you to slowly build a running base.
If you’ve got a good running background then the Mike Foote Big Vert plan will be a great one. It’s one of our most popular plans and has been used by hundreds of folks with great success. But it is not for a newby runner.
I hope this helps.
Scott