I must not have much to do replying to all these near zombie threads - time to get busy. The reality, is that I have the burn on my mind, and it's 10 deg outside (fucking sick of this winter!!)
If you are worried about cold, I'm guessing you haven't camped much. Not to worry, it's pretty rare for a night in the low 40s, and I don't think this has happened in a few years now. If you are in an RV, they tend to hold some heat from the day time anyway.
Pretty much any sleeping bag and an extra blanket will get you there. And if you're worried, just bring another blanket/sleeping bag. No need at all to bring a heater.
When you go to bed you'll be exhausted, so just get in your bag and go the fuck to sleep. When you wake up (unless you're mental like some folks getting up a 6-8am like you do in the default world) it'll be 70 degree or warmer by the time you wake up and you'll be sweating.