Highway 20 west from Williams Lake is paved all the way to just east of the Heckman Pass that descends (steeply) into the Bella Coola Valley. However as you are only going as far as Anahim, nothing to worry about.
Expect gas prices to be expensive as you head further west out of Williams Lake. IIRC, last year at Anahim Lake the price per liter for gas was around $1.60 per liter (approx $7.75 per gallon.) One year later, expect higher prices. Currently in Williams Lake, the cost per liter is about $1.30 (approx $5.90 per gallon.)
West of Williams Lake, there are gas stations (the ones I remember) at Alexis Creek, Nimpo Lake and Anahim Lake. There may of been a couple more but I did not stop at as it is only about 200 miles from Williams Lake to Anahim then it was only about 90 miles from Anahim to Bella Coola. Be forewarned that these are small remote communities with only basic services and they tend to close early so get your fuel more early then late.
For camping with the large RV. There is Bull Canyon Provincial Park just west of Alexis Creek. I seen some larger RV's so I cannot see any problems with your RV. There are also a number of Forest Recreation Sites along the way but they will probably not accommodate your RV and toad. As I only boondock, I usually don't pay attention to private campgrounds et al so perhaps others can chime in here. That all said, there are plenty of places to pull off the highway in turnouts, side roads etc and you will not be disturbed and it is safe.
As for changes since your last trip many years ago, your drive along the Chilcotin Highway 20 will show that life has not changed much at all. This highway is one of the best kept secrets in Canada.
Lastly, consider purchasing the book
Cariboo Trips and Trails. Although almost 7 years old, this book is the bible for venturing into the Cariboo area of British Columbia. Note that the link will take you to amazon.ca as .com lists the book but at a more hefty cost and it is used.
Enjoy your trip. Enjoy the memories.
Let me know if you would like any other info, I will be glad to share.