Yup, finally figured it out. Again, not very clear on the instructions -- I had to go find a youtube video of someone else doing it to figure it out (and he couldn't figure it out for ages either). Still, now that I'm past that stage, this is fun! There were no mobs for ages and I started to assume there simply wouldn't be any, though, and then suddenly there were 2 creepers, a skeleton, and a zombie all eating me. When I died, they guarded my stuff. Frustrated and not wanting to lose my progress while I was still learning how to play, I just set it on peaceful until I get my bearings.
What determines whether mobs can spawn, anyway? They didn't spawn until I put some wooden planks down to make a floor in the big open hole so I didn't fall to my death and had more room for tree saplings. Is there a way I can calculate it so that they don't spawn when I'm not ready or where I don't want them?
I like all the mods. They work really well together. I like the quest system, too. I don't know how it would be possible to survive with mobs on, though, at least in the beginning. I did finally realize I could make wooden armor, but it will be a long while before I get enough dirt to make enough stone to make a furnace so I can make torches, though.