Most of this stuff is the same sort of malarkey that they said, or are still saying, about ethanol. This B.S. about new injectors, lines, filter, and stuff is just someway for someone to make easy money off of you. You may have to change you filter out at first. That's about it.
But, by now you have been running bio-diesel in your rig and never even knew it so I'll bet you have the system acclimated by now. A fungicide is a good idea though. Especially for RV's that set around a lot and don't get used.
I live on the farm. We have used 1000's and 1000's of bio diesel in every type of diesel engine without issue. But, we do put a fungicide in the storage tanks.