What kind of shifter is on it. Is it clutch shift or shift rod running down to gearbox.may be as simple as having it in neutral.been a while since I've done it can't remember very good.
After u take inspection plate off there should only be 1 bolt to disconnect the shift shaft.take your model# to searspartsdirect.com. they have parts diagrams that show everything.
I went on sears site the diagrams are fuzzy for my model doesnt show it well enough to tell. Only thing left is to unbolt powerplant and see if driveshaft will release that way