I cut off the old old flange at the elbow and scored the junction of the remaining flange with a knife. Then I used a flathead screwdriver to peel the remaining flange off the elbow (not as easy as some may say). The knife scoring helped guide the peeling. I sanded, cleaned, and glued the new closet flange into place.
I bought a Caroma toilet with the offset outlet. It's nice because the outlet is attached to the flange separate from the toilet, so you can check for a good fit.
If I were to do this again I would cut off everything as mentioned by TheEPlumbers, and then use it to beat the previous owner