I have just completed a complete engine rebuild on my 1700 and it is not that hard to split this tractor.  The plug that is leaking is a core plug.  The only way to replace it is to split the tractor, remove the flywheel which has a 2 1/2" nut torqued to 325 ft-lbç—´, and remove the 3/8 adapter plate. Removing the flywheel and then torguing is the most difficult part.   If you are not comfortable doing those tasks then you will have to hire some one or take a chance on a shortcut.  You could try to dimple it more and use the stop leak as JC recommended.  That could buy you a couple of years before it starts leaking again.  The choice is yours but I would lean toward the shortcut.
Russell