What should I know about Hwy 12 through Idaho?

I have a question for those “been there done that” folks here. Come early September I’ll be heading east to South Dakota from Port Angeles WA. For various reasons I want to cut down though Washington and catch Hwy 12 across Idaho to I-90. I drove that stretch of Hwy 12 back in 1998 when my son and I were returning to Illinois from a Washington State mountaineering adventure. My problem is I wasn’t viewing the road through the eyes of a guy driving his 33’ home-on-wheels with his toad hooked to the rear. I looked it over on aerial photos and while I could see some rapids in the adjacent river I didn’t see much else that might indicate any long steep topography or switchbacks. I seem to remember that the entire road was paved and somewhere on it is a Forest Service campground. I do remember it being a very beautiful drive. So far on my Grand Western North American Tour and shakedown-journey, I’ve driven over California’s Tejon Pass with no problems, as well as some interesting grades on I-5 and Hwy 97 north of Redding without problems. However, I do remember Hwy 12 through Idaho can be a pretty lonely stretch of road. Is there anything I'm missing that might be a problem driving the behemoth?

Steve