I just came south down 97 starting from Biggs Junction down to Weed, Ca. last week. I also was towing a fifth wheel the size of yours. As others have said the road itself is not bad. It is a two lane highway with a 55 mph speed limit that goes through the middle of nowhere once you get past the Madras area approximately. Make sure that you top off the tanks because there is a whole lot of nothing in between there and the junction with I-84.
Just got back from Kalispel on Sunday. There was a little construction going on near Kalispel but it was nothing major. There was a section where one lane was closed and the speed limit was 35 mph. Other than that it was smooth sailing.
I drove it a couple of weeks ago pulling the fiver. It was tight in a couple of places but doable. The biggest problem was a trucker that passed my rig and another rig I was traveling with during that section going about 70 mph. I thought he was going to blow me into the cement barriers. take it easy and you will be fine. Have a nice trip.