It probably a cast iron flange and a cast iron drain pipe that are connected with a lead/oakum joint. While technically possible, it may be more than you want to tackle yourself. Leak/oakum joints were not intended for a week-end warrior. The smart thing to is to have a plumber remove the old flange and replace it when you have finished the floor repair. You can look into past ports about how to drill out the lead, etc if you really want to do it yourself, but if your time is worth anything, get a pro to do this...I wouldn't try it, and I'm a confirmed DIYer.