If you're going dark you'll want to prime the walls grey, or have the primer tinted with your color of choice. As an example when I painted my house the primer was tinted 50% the color of the house paint.
My walls are going to be a dark red, with a dark brown ceiling. I had my primer tinted grey.
Talk to the folks at the paint desk. I use Zinssner 123 primer, since my uncle is a professional painter (25+ years) and that is his primer of choice. The paint for my theater came from Miller so I used their primer this time around, mainly because they were having a sale.
Are your walls smooth or do they have a texture to them? Orange peel, knock down, ? A good 3/8" nap roller will work well for most walls. Matt finishes show smudges very easily, where a flat is more durable. Eggshell is not bad but does have a bit of "sheen" to it and would likely be a little reflective.