Looking for lower unit on a merc 7.5

I am looking for a lower unit on a merc 7.5

I have fixed many things in my life and turned a lot of wrenches, but I have never worked on a boat motor. I bought a boat this weekend and it came with a Mercury 7.5 The previous owner said that the "lower unit is trashed". I would appreciate any advice on how I should fix this problem. Where do I start?

Thanks,
Kevin
West of Little Rock

mercury outboard lower unit parts - Yahoo! Search Results

google more and you'll find more places than you can shook a stick at. google service manuel for mercury 7.5 hp motor and include the year and you'll find a book to help you.

I do outboard repairs on the side, I have a 7.5/9.8 merc gearbox that I believe to good internally that is for sale if your finding yourself in need of parts. I believe all it needs is to be re-sealed and would be a good gearbox.