Petrie, let me start be saying that, yes this is a site to get help on DIY plumbing jobs, and to your credit, you have asked for help before getting into trouble. That said, sometimes the best advise we can give a DIY is to hire a plumber. This will not be a difficult job for him, he has to know how, and the tools to do set your flange right. That last thing you want is a makeshift job on a toilet drain that causes problems. Forget about the adhesive and other gluing PVC to cast iron, etc.. I do realize that you and I look to DIY as a means to save some money and there's nothing wrong with that. But, there are times to be frugal and there are time to pay the man. I do believe this is time to pay the man.