This was the trickiest repair so far.  I dropped the lower unit to check everything out and replace the impeller.  The lower unit was stuck so I needed to use a couple putty knifes and wood wedges to get it to drop.  The two locator pins were corroded into the housing.  I was afraid the shaft was stuck.  I had read horror stories about cutting the shaft to separate the two.  
Everything else came apart ok but the impeller's woodruff key was pretty corroded and I was afraid it could spin inside the impeller.  I ordered the key from boats.net and took it all apart again.  The new (and old) are steel.  I tried round punches, vise grips, and dikes to get it out.  There wasn't much to work with because it was corroded and already rounded over.  I took out the dremel with a fine cutoff disc.  Split the key in two and it came out easily.  The new key was pretty tight.  Had to smack it in with a brass hammer.