Replacing swim platform brackets on a MC

Anyone changed the boat-side swim platform brackets on a MC?
I have to replace the brackets on the boat side of my MC, so I am interested in what kind of job I might be getting into.

Do the screws/bolts have a nut on the interior? I didn't see any from within the boat, so I am assuming they are Lag type bolts.

Can anyone reccommend sealant or epoxy that would be best for this application?

Thanks