Yes, it is a long shaft engine. Being a long shaft engine doesn’t really make much of a difference, except for that spacer tube between the impeller housing and the exhaust hsg.
Using the wood as a wedge probably won’t be too effective, the wood will probably just get shaved down as it is driven between the housing and extension. Perhaps you should try removing the four screws holding the extension housing to the exhaust housing, letting it slide down, then prying in between the extension housing and the exhaust housing. Put the wood up against the exhaust housing and pry between the wood and the extension housing. The extension housing is easily replaced if damaged or gouged up. You will need a couple of decent prying tools, or very large/long screwdrivers.
Again, it is the impeller key that is keeping the driveshaft from just pulling out of the gearcase. Prying will eventually force the key through the aluminum housing. Or, perhaps you could get in there with an air chisel and just break up the aluminum impeller housing releasing its grip on the impeller key. Needless to say, the air chisel is pretty harsh method, so care must be used to avoid damaging the gearcase housing. Again, it is no big deal if the extension housing is damaged, it is easily replaced with a used one. The aluminum impeller housing can be replaced as well if it gets “sacrificed”.
Once again, that reverse lock is automatically engaged when shifted into reverse. So, try to push the gearcase back up into place so the gear shift can be placed in neutral which should release the lock. If not, just get underneath that stern bracket with a screwdriver and pry the locking lever up and off the trim pin so the engine can be tilted up.
A couple of seasons of salt water use is usually all it takes to rust up the driveshaft/crank splines, unfortunately.
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