Chris,
Joe Friel's "Training Bible" is excellent but also check out his "Cycling Past 50". It has a lot of what's in the Training Bible but I see it as a friendlier format and not quite as intense. Look a them both to see what suits you better. BTW, You don't have to be 50 to get Cycling Past 50
Oh, and yes get a heart rate monitor. Any training program you'll follow will have you in target HR zones based on the goal of that particular workout.
Michael