Re: Mil or MOA ?
There are spotting scopes with MOA reticles, US optics is one example.
If you had a spotter, wouldn't he know what adjustment to call windage and correction/holds for you?
Re: Deal or no deal
I would say no deal, keeps searching for a good deal or negotiate him to drop the price a tad. For example could save money if the rings don't fit your scope.