1984 evinrude super 40 impeller change ?

[Roy Wirebaugh]

I'm wanting to change the impeller in my 1984 40hp evinrude model# E40RWCRA. I bought the impeller already. Do i need to change the impeller housing seal also? 2nd question. Is this change any different than changing the impeller on my 66 20hp Johnson? Thanks, Roy