Well...if the second ignitor is good you now have a spare....in a
couple of years the current ignitor will go bad...maybe sooner if you
didnt get it put back just right.

I worked for the gas company years ago and we had to go out and inspect
gas furnace installations....I remember this one company always had a
lot of trouble with the hot surface ignitors in their furnaces being
broken even before the furnace was put into use. They would be broken
by the rough handling the furnaces received from their installing
personell....dropping the furnaces etc.....

silicon carbide is fragile.....and the problem with oil from your
fingers is this....it causes the silicon carbide to heat up at a
different rate where the oil is....it makes it not heat evenly and this
puts stress on the fragile material.