Running a 306 TD on veg is one of the easyest things to do.
To start just brim the tank with veg, and when it's empty change the fuel filter.
That will clear out all the crap from the fuel system, after that change it ever 10 or 20K.
It won't damage the seals on the pump
You won't need a pre-warmer or extra heat exchanger - as both are included on the std model.
Mix with 5% petrol in the winters to keep it fluid.
Add in mineral 2-stoke oil at 1:200 to increase the lubrication of the pump as thinning petrol decreases pump lubrication.
I've been doing this for the last 8 months on my 306 TD, zero problems