Broke the OPSU.
 

'94 4.0 4x4 AX-15.

Was doing an oil change today and I reached both hands in the bay to twist the oil filter off. When I got it off I looked to the side to see a broke sensor which I guess was the sending unit even though I've never seen one or replaced one. Sure enough I turned it on after everything was buttoned up and my reading is 0.

The rubber is torn but it is still holding on. The torn rubber is thin, and when you look inside I see a green cap. I have done some reading and for some people it leaked like crazy but mine isn't broken at the metal and I haven't driven it three times with no leaks.

What do you y'all think? Should I replace it asap or order one from rockauto and not worry about it?

Just a matter of time if its broke b4 it leaks replace asap if dd if not order and park it.

Will do. How will I know if it's the right one? I know they have a different number of pins, etc.

Also what about switching to a mechanical gauge?

Look at your plug make sure the one you buy fits. As for mechanical that's a owners choice.