If u buy tickets online..do u have to stand in line??

Yes, but the check in is fairly quick. If you want to avoid a large line, go early or during the week

Tried to go today but the line was all the way around the corner of the building

Yes, its first come first serve. Go begining or mid week for smaller crowds.

To check in, yes

Unfortunately, but it goes fairly fast. Go during the week if possible.