The whole affair is a sleeve and you have to replace the whole sleeve. That's a press or you can heat it and slide it off. That "Slide" is a very loose term. I'd be tempted to just leave it. Don't know where you'll find another without buying a donor gun. The trigger is easier, just replace the parts.
Here's the sleeve... https://www.libertytreecollectors.co...&idcategory=17
They have the trigger and sear bits too. Don't know if you can import them though...