You find them both and look see if they are leaking.
check your oil to see if you have coolant in it. if you do your intake gasket needs changed.
check and see if the old rubber gaskit is stuck on the oil filter housing
The oil could be getting into you coolant system. Check to see if your radiator fluid is milky brown.It could be a leak that only happens when your jeep is in motion.
Check coolant leaks with a visual inspection. Clean the engine, then see where the coolant reappears. Look under the water pump. Check engine oil to see if coolant is leaking into the oil.
you can take oil and put it where you suspect there to be a vacuum leak. If there is a leak the oil will be pulled into the engine or hose
Clean the 1994 Sable transmission at a car wash. This will make it easier to find the leak. Keeping the fluid full, check the transmission frequently to see where the leak is.
check to see if the previous filter gasket was left behind when you did the last oil change. When two of the rubber gaskets are present, you get a pretty good leak and you can't see it til you remove the filter and check.
Check the oil cap and the drain plug, as well as the oil filter.
You may have blown a head gasket, check you oil to see if the antifreeze is leaking into there.
You cannot check the fluid level as the transmission is a sealed unit. A GM dealer can check it if you have a leak. If you have no leak then it is fine.
An oil leak is always going to be out of the engine as the engine contains oil and the car does not. I think you are saying you are loosing oil with no apparent leak. If that is the case the engine is burning oil and that is why you see no leaks.