Front tine garden tiller?

I have an older front tine garden tiller which is gear drive by a belt.the gear box which drives the tines
leaks fluid.I use 90w gear oil,and it leaks out both sides of shaft.It has a 1/4" npt.plug that fits filler hole.
I plan to put a 1/4/1/8 bushing to replace plug with a grease zerk.I plan to fill housing with grease.Would this
protect the gears,I don't know what is involved to replace both seals? I do not know the made of the tiller