Bought a 3206 last fall, (No SN to be found) had a leaking hyrdostatic, old owner "topped it off every so often" I climbed under it and cleaned off the amazing amount of grass blocking everything including the fan

I could not locate the leak. Well now that snowblowing season is over I tore it down:
https://photos.app.goo.gl/coQ9dRWwrajPNY828
I had just about given up when I saw a little seapage:
https://photos.app.goo.gl/DXA91kCDHgJzyUyQ8
https://photos.app.goo.gl/qQDaSQ8AaUzgsptg9
(Notice it between the black and silver parts in the crack)
So my question is do you guys think its the o-ring in behind there? Do I need to pull the other lines off to get it out to change the o-ring? Will I need to buy other orings if I need to pull those lines out?
https://photos.app.goo.gl/4n2RvAGjeM6eLWvZ8
I think I need two of these at least:
https://www.partstree.com/models/320...ansmission-19/
22
O-Ring
Part# HG-9004100-1430
Your price: $2.88
Can anyone tell me what else I will need or any special parts?