Good for you for ramping it up!

I wouldn't totally let go of speedwork. You don't want to over do it. But you could indeed do some intervals, or hill reps, or a tempo run (warm up by running gently, then run faster for, say, 10 minutes, then gently again). The idea is to push your comfort level A LITTLE, and once a week. Don't go crazy or you might indeed hurt yourself. (Because unlike cycling, running speedwork can be tough on unaccustomed joints.)

Otherwise there are gazillions of decent training plans for beginners online. I agree about adding distance progressively, and planning rest weeks (once every third or fourth week). And don't forget to taper (i.e. gentler week - but not inactive - before the race).

Enjoy!!