Hi, wondering if I can sub bulgur easily for the buckwheat. I was in a Turkish market and bought some. It’s whole. Should I toast it first?

The cooked bulger would probably work nicely in this dish in terms of texture and flavor.
Yes, good idea to toast it first (will give more flavor), but not required.
There will, however, likely need to be changes in cooking procedure.
The original buckwheat is either a grass or an herb (I've seen descriptions as both) and cooks relatively quickly, while bulger is a wheat and will need both more water and more time to cook.
Good luck with the resulting modified dish!