after you remove the ge-0/1/2 ge-0/1/3 configuration what interfaces if any show up in
show interfaces terse
After the configuration removal can you insert the xe optic cable and run again
show interfaces terse
to see if the interface shows up as xe
I've not use th ex3300 but on the acx platform with the dual ports the interface type ge verses xe is trigged by the optic being in the slot.