Eb3 pd may 2017 mexico, expired medical, interview date not given

[litleboy]

-filed 485, priority date of march 2016, there was an error on website stating that my date was current and that is why we filed, months later we got a letter refunding the fees and tellin us to file when visas precede the priority date.

-Filed 485 again and priority date now was may 2017
-march 23 2018 got update, I will be getting an interview date

My medical are well expired, should I get new medical before I get my interview date?
How long does it take to get a date for the interview after they tell you that they are ready to schedule?


Thanks