I just did this same job on my 175. I also replaced the seal housing. One thing that made getting the new housing and o-ring in a little easier was to tap it in up to the o-ring, put the plate on, then snug it up to the housing with the spacers and nuts to keep tension on it as you tap it in the rest of the way.
Good job! I’m priming myself to do this on my ‘95 MF 240 which is leaking like a sieve now. Did you only do the o-ring or replace the whole bearing seal assembly?