I've heard that is the 'right' way to do it... but have never made sweater in pieces myself.

most people say you should.

yes. YES. yes.

i've heard that it makes seeming up easier

Okay, this is my first sweater so I wasn't sure if I should block first, or block after sewing

Yes, blocking makes it easier. Good luck!

I just did...steam blocked...and it did help flatten it out

I took a class with maggie jackson and she said she never does unless she has too