You might try the county extension number. I think they should be able to direct you to local businesses.

Sorry I cannot help further as I'm not familiar with your area. I live in southeastern PA.

Here is a link that might be useful: County extension service

I'm really hoping for a personal recommendation of an actual nursery/garden center. I'm not looking as much for what plants will work (most of what I want would grow in New England, so should be fine here); I need to find one place where I can buy everything I need. I hate having to go to 10 different places to get what I want.

heh heh. I make a point out of going to 10 different places to get what I want.... Usually I didn't even know I NEEDED it until I get there.

If you don't like the county extension advice (most CE's offer great -often free- expert services that are not taken full advantage of) just go to a box store.
Pull up to HDepot, have them load a few bags of topsoil, mulch, plants and be done with it.

In your first post it sounds like you want expert local advice and varied selections (county extension territory ->not box store!)
If all else fails the yellow pages should give you a start.