Had some minor corrosion so took it off
any sealant that needs to be used or the oring get the job done alone?
and how tight do we screw the cap in?

Google says 20 ft-lbs...someone with a service manual can confirm.

The book States 20 lb

Need some polishing/smoothing on those surfaces where O-ring and seal surfaces

Before it goes back together, have you removed the back cap to inspect?

20Ft Lbs and A Thin Layer of Perfect Seal to help with seal and Corrosion .

no i did not... nothing on the magnet when removed to drop oil so... should I really?

ok good info thanks!

It cost nothing to remove, but there might be some leakage there, and could advise of future issues. Same torque spec