When my school was a Reading First school, we had to use the reading program with fidelity (or an equivalent of that word
The program was scripted, and the powers-that-be would come in and make sure we did exactly what the teacher's guide said and in the exact order. On Day 1 we would do such and such, on Day 2, such and such, etc. It was really ridiculous, because they treated us as if we were just factory workers instead of professionals.
We also had to use the same language (scripted), but that did not work with my little ELL darlings as they had no clue what I was telling them. One year they required us to use every page in the practice book, the next year they told us not to use the practice book at all. We also had to use the resource books exactly as written (ELL, special support, advanced, etc) but there was no time to use it all, so we conveniently misplaced them.
I don't know about your situation, but I would take the most important parts of the teacher guide, and then use your judgment to add your own stuff. You know your students best, and know what they need more. Language arts programs are geared toward the generic student, and I don't care how good they are, they cannot know what your students need.