I attempted to change gear oil in lower unit and made a big mistake it seems. I accidentally removed the wrong screw from what I thought was the drain pin. I now found out it is a "clutch pin" or "shift pivot pin" or something. When I put the screw back in the "propeller is always in gear". It didn't make any funny noise ( I don't think). How do you get the pin and everything back in proper alignment? Should I take it to a qualified repair shop? Have I damaged the lower unit?
In addition to the advice already given, This is what happened;
The Coupling (#49) will have come loose and Yoke/Shift-pin has fallen inside the LU
Here are the steps to take;
Remove/drop the lower-unit
You'll have to remove the gear assembly reverse/prop-shaft/dog-clutch but you can leave the Drive-shaft/pinion-gear and forward-gear.
Tilt the Lower-unit with the opening to the sky and move it around, with aid of a flashlight you will find the Yoke that has fallen off the shift-pin when the Pivot-pin(#32) was accidentally removed.
Now the tricky part (as the yoke is not magnetic) to fish it out trough the prop shaft opening from the forward-gear.
Once the pivot-pin is back in its place and the Coupling moves back and forth as it should, apply a small amount of marine-grease on the yoke/shift-pin(to keep it from falling off) also make sure the yoke's opening is facing down
Have the coupling facing toward the shift-pin and yoke(moving it in place by puling/pushing the Shift-shaft
now slowly start pushing the prop-shaft and all parts attached into the lower-unit.
Make sure!! the yoke lines up with the coupler behind the forward-gear, when it latches together; you'll see the shift-shaft come up
Patience & steady hands are required (results may vary)
Good luck