Here in Alaska we don't use tube removing tools, those are for pansies anyway. We just set the case on a stump and use a .223 high powered rifle. The extreme cold makes the tube real brittle and you just aim real careful and BLAMMO. No more tube. Don't miss. Or set the case on a woodstove for a minute to get it good and hot, then use a triangular file, jam it in the hole and unscrew that sucker.
It's slicker than wolverine snot on a doorknob to put the new tube in, just goo the threads up with Loctite Blue and screw it into the case. Then screw the crown onto the tube, and use your manly thumb and index finger to screw that sucker down tight. The crown will bottom out on the tube, then the tube will screw further into the case, until the crown touches down. Bingo, perfect install every time.