Lower Unit Issues

[macksk8]

I just recently purchased my first boat. It has a 1977 Evinrude 70 hp outboard that I believe is leaking lower unit oil. The oil was changed before the winter, and after running it this week hooked up to the hose I decided to check the lower unit oil. It was milky even though it only ran for about 15 mins. I am also noticing a large amount of thick black milky oil coming out of the prop after I ran it. Is it safe to say the leak is somewhere in the prop shaft seal or o ring? Or could it also be at the top of the unit? I was really hoping to avoid issues like this on my first boat. I am debating on whether to pressure check the unit myself and repair it, or take it in to get it done by a mechanic. Does anyone know about how much it would be to have all the seals replaced and water pump done?