I bought this for $15 at a flea market.  

I took it apart and brushed it down.  Operates perfectly when lighting manually.

However, the piezo will not ignite the lantern.
It's been discontinued so no replacement parts available when I called Coleman.

The gap between the electrode and flat bar is perfect at 1/8" (per manual).

The electrode and piezo are combined, and I took it out, held onto the piezo, and hit it and it gave me a mild shock.

Anything I'm missing here?

Close the gap down 
Might have a loss of continuity somewhere along the line, clean any contact points inside of igniter mechanism, that you can

If I test the electrode (ohm it out) will that tell me if the electrode is good?

Ok I moved the electrode around and the flat bar and got a spark to jump and actually lit it three times.

This requires a lot of mojo and timing.  The third time I allowed too much propane to build up and singed my hair off my hand.

I'll just light it with a lighter

Sometimes a 3 dollar extended lighter is better than trying to fix something ha ha