I think Princess Auto has their wet tile saw on sale again. $60 for a 7" saw that comes with four diamond blades.
Minimally I'd cut off a small healthy section so that you don't loose all of it if you cant stop the spread. What has occasionally worked for me is to just siphon off the infected area at least twice a day until the recession stops. However if you're not going to be able to access the coral until the next time you're home there may not be anything left.
For instance this coral spent too long in transit in a bag that was too small with too little water in it. I was able to stop the die-off without cutting the coral by removing the tissue that was dead with a turkey baster.
