Lots of great advice but I just wanted to chime in that the temps will most likely be just fine -- even for a native Texan. :)
My wife's from South Texas, where temps seem to reach 9000* -- to me at least.
I've been surprised by how long our propane lasts, and the cheap 12V coach battery. We've camped in freezing weather; we've all got nice sleeping bags. It seems like all I had to do was fire up the furnace just to take the chill out of the motorhome.
If you're driving right up to elevation, be sure to bring SPF50 sunscreen and plan on drinking lots of water. Staying hydrated is key.
