I think it would be better for you to buy a mill, and crush the grain when you need it, than to get an entire bag crushed. I think you'd probably have settling issues if you didn't use the whole bag at once.
What if you wanted to make a recipe with a different base grain like pils or something. Then you'd have to go back to the LHBS's crush, and your efficiency would probably drop.
Which mill is best. I'm pretty sure that you'd be happy with any adjustable roller mill. I have a Barley Crusher, and I chose that one because it was the least expensive mill that was ready to go out of the box.
Here's the adjustment on the Barley crusher. There's one knob on each side.