No, spec has nothing to do with dialog choices. Your dialogue choices, however, will typically be light vs. dark side options. There is no real difference light vs. dark, it's simply a matter of preference. Although certain companions that you will get have their own preferences. Check out the codex which is stickied at the top for your first few levels (till around mid-teens). Then as you see what you like and what you don't, come here and look at various spec posts. Don't worry about gear just yet, just take the quest gear you are given. As for weapons, you will wield a one-handed lightsaber in your main hand and a focus generator in your off-hand.