I muted this thread, then thought better of it… so here’s my last input:
Learn French as quickly as you can…
At 40 you are young enough for the brain to take it all in… hurrah.
Contact your Mairie, introduce yourself and explain your plans/hopes and ask them what Planning Permissions you might need from them…
“Notary” is not a word I know… Notaire I do know… so I suggest you use the word Notaire (no matter whether using French or English)
You mentioned fruit trees… so I didn’t think of walnuts… you need to be very specific about trees as there will (probably) be different requirements for different species…
Glad you’ve made a friendly/helpful contact in Grenoble… but… as already said… you need to make contact with locals (possibly introduced via your Mairie) and the AOP Perigord will be important for any future fruit/nut/ business
and I reckon the Forestry Agency if you are doing any woodlands…
wishing you the best of luck… 
over and out