What if I'm still waiting in line when the polls close?
So long as you are in line to vote at the time the polls close you will be allowed to vote.
If I chose a party do I have to vote for all of their candidates?
It depends on the election. In primary elections, you can only vote for candidates from the party to which you belong. In general elections, you are free to vote for anyone you like, regardless of their party affiliation.