Cast iron closet flange questions

[BimmerRacer]

Hello,

I am starting a remodel of our basement bath and have some questions about the closet flange. The bath previously had carpeting and the toilet set right on the concrete slab. I am planning on using Ditra and tile so I am looking at 5/8" of finished floor height. It's my understanding that the closet flange needs to sit and be supported by the finished floor.

Below are the pictures of what I have now. The flange doesn't appear to me in too bad of shape but it's not leveled and the back side isn't supported. I also don't think it's screwed into the concrete.

So, my questions are:
- is it best to remove the existing flange and if so, how?
- finish the floor as planned and install a new flange? if so, what kind?
- if installing a new flange, I am assuming the leveling issue will transfer over since I am assuming it's the sewer pipe thats actually isn't 100% vertical.

Finally, is it doable a doable DIY? or is this better left to a plumber? I have done plumbing with PVC/CPVC, PEX, and copper but to be honest this kinda scares me!

 

[Reach4]

I would not replace it. I am not a plumber. Is the flange held strongly? If so, maybe just use two wax rings or two Saniseals. It is done frequently, because recessed toilet flanges, while not ideal, are pretty common.

Another alternative is Hydroseat over the new floor. http://www.danco.com/product/hydroseat-flange-repair/ That gets a wax ring between the old ring and it, and another wax ring or waxless ring goes between the Hydroseat and the toilet.