lower unit oil leak

uh oh...oil coming from the forward cooling water discharge hole..lower unit oil leak?..manual says check seals and shift boot....how bad can it be total lower unit rebuild?or a common seal easy change?.1995 tlrt 130 800 hrs appr. confirmation was draining of oil it looked like a gray milk shake not all but most ...any help thanks

[boats.net]

If it's used in saltwater it can be difficult to get apart, may need a torch and strong pullers.