And, save the old motors.
If the stove is used, the previous owner may have used the wrong lubricant, or none. However, you may be able to revive them. I've rescued many old ball bearings in motors and tools by carefully re-oiling them with the correct oil for their application. In fact, I just stopped a screeching bearing in my 30 year old high-speed hand grinder last week. Bearing was dry, but not worn to the point of needing replacing.
Don't use motor oil in ball bearings. Some of the additives, especially detergents in it, can get gummy with age and heat.
Ask the Hitzer factory rep what oil they recommend to use for that application. If they don't know of any, then use air compressor oil. If they do recommend an oil, only use that one.
To re-oil sealed bearings, using a point of a knife, or needle, carefully lift up the outer edge of the rubber side seals on the ball bearings. Drip fresh oil onto that slight gap and it will naturally wick into the bearing. Spin the bearing by hand so that fresh oil will loosen and help flush out old gummy oil.
Working fresh oil into the bearings, you may find that the used motors start working again like new. In which case you can put that motor back into service, or if your not comfortable relying on it, at least keep it as backup to a new motor, . . just in case.