Three questions. 1. How hard would it be to get 19 years worth of Gmail to Fastmail? 2. I have 4 different domains worth of mail all coming in to one mailbox?

Three questions. 1. How hard would it be to get 19 years worth of Gmail to Fastmail? 2. I have 4 different domains worth of mail all coming in to one mailbox? Would this be an insane cost on Fastmail? 3. For those of you who have already switched from Gmail -> Fastmail, is there anything you miss after the move?