1. You *must* have the key/ignition tumbler in the second detent position in order to be able to successfully release the large black plastic electrical connector on the back of the ignition assembly. This is because the connector itself has a hole (shaped like this: |----| )in the center of it which is the receptacle for a pin that is the same shape. When the key/ignition tumbler is in the first detent position, the pin is in the hole and turned and thus is holding the connector in place so that it cannot be removed.
2. The new key/ignition tumbler’s pawl (the *whole* L-shaped thing on the side of the tumbler) must fully retract on installation and fit into its spot perfectly in order for the black metal ring to properly situate. If the ring’s detents don’t line-up fairly closely with the key positions as it did when the car was new or whatever, try the installation again because things are not right yet. In my experience, there will likely be an audible click (probably the pawl completely popping out of the side of the tumbler) when the tumbler and ring finally situate properly and as they should be. If you cannot turn the new key/tumbler with it and the ring installed, things aren’t right – try again. REMEMBER, to release the electrical connector on the rear, you must have the key/tumbler in the second detent position.
My tumbler lasted 245,000 miles/25 years and 9 months. Not bad. In fact, nothing short of remarkable. Just consider how many times that thing was turned. Whew