Seloc after market service manuals are on sale here on iboats. I had an OEM and Seloc for my last engine and I liked the Seloc better due to better explanations and pictures. You can buy one or rent one and view online. I did the rental and it was great and I had immediate access which was important.
Corrosion is going to be your enemy. Corrosion in getting fasteners undone and in getting the lower unit to drop down from the mid section. Use a quality penetrating oil, like PB Blaster or better, Something like WD-40 is not your best bet for this.
Next is to use impact rather than raw strength to dislodge bolts and nuts. Spray fasteners with the oil and let sit, overnight if you care...longer the better. Install the proper wrench on the fastener and take a hammer to the handle of the wrench using just enough force in the smacks to get a result. Old hardware likes to shear (bolt shanks break due to corrosion resistance around the threads) and you have to be careful to be successful. Prior to reinstalling the fasteners chase the threads with a tap (best) or a wire brush to get the corrosion out. Then apply blue Locktite which will act as an antiseize and thread locker (auto parts stores carry it...may be a different brand of thread locker but blue is the color you want...it's designed to be reworked, not permanent locking like red).
Most hardware required for servicing is obvious to the naked eye except for one hex Allen screw. On the top rear of the mid section, about 2" above the horizontal plate (antiventilation plate) which is just above the prop, is a plastic cap over a hole. This is access to your trim tab. Mark the position of the tab (L to R) so that you can get it back in the same position upon reinstalling. Remove the screw in there which will allow you to remove your trim tab. Then look up from under the antiventilation plate in the area that was covered by the tab and there is one more hex Allen screw in there that has to be removed to drop the lower unit.
Once you are confident you have all the hardware removed, separating can be a chore. Just remember that you are dealing with cast aluminum and it is not all that thick in most places. It doesn't like you beating on it or prying against it. It's brittle and will break on your so you have to be careful prying and banging. One technique used by some is to suspend the engine upside down with a rope tied around the LU just above the prop. Top of engine, should be cushioned against damage and be about 1" above the cushioning so that when it breaks free it doesn't have far to fall. Archives have tips to help in getting through this part.
Before reinstalling the shift shaft and drive shaft, clean up the splines and apply grease to the splines, not the top of the shafts as too much grease can prevent complete mating.
Archives herein have hints here too.
While you are at it, change your lower unit oil. Manual will direct you in that too and WM has the oil in the sporting goods section. The manual will also tell you how to set up your shifter for proper mating so that the gear you select when finished is the gear the engine gives you.
Good luck,
Mark
