I'd been hoping to hit Nfld as well this summer but that went out the window. Wife had three weeks or so which I didn't think was enough time to do it all (we'd been east before so could skip some). Nfld itself has to be at least three weeks imo. Gros Morne and L'Anse Aux Meadows are key places on the west side and don't be fooled by the maps. It may look easy and fast but in reality will take longer than you'd think.
Cape Breton Island is worth more than a few days as well. We took the overnight ferry from Portland to Yarmouth arriving crack of dawn. Loved the Ingonish area.
My suggestion would be to see NS, PEI and NB and save Nfld for another trip when you have more time.