Getting the actual rim off is easy. The most basic way is taking a box cutter and going back and forth until the rim gets loose. It's much less work to use a planer until you almost hit the glass (go slow and it will be obvious), then use a razor blade or box cuter to get it off.
The really hard part is making it look nice. I would get a 10 pack of razor blades minimum to get the excess silicone off. I only use one for about 3-5 minutes before switching to a new one. I save them because they are still good for general use but you need them at their sharpest on the glass. I won't go into detail as it's been posted many times but you basically use rubbing alcohol as a lubricant and go back and forth with the razor blade.
Then you need to finish the top edges, most likely as they will be sharp, and not totally even. I use a sanding block with about 300 grit to start, moving up to anywhere from 600 to 2000, depending on what I have on hand.
It has taken me about 10-15 hours per tank (only have done 2) to get it right. Some members have used various power tools to speed up the process, something I was just too scared to do. That seems really long but I have always done it during a dry start so do an hour here, and hour there, not a problem. I may be exaggerating the time but to make it look like a rim was never there, it takes time.