I've changed several. Just last weekend I changed the cutting edge on a neighbor's slip scraper that was welded on. All the methods mentioned here will work fine. Using a cutting wheel on a grinder will take more time to cut off the old one, but will generally give you a better looking finished product. If you have anyone close who can use a plasma cutter to cut it off you may want to see how much they'd charge to do so. I use my plasma cutter and if gives a good clean cut without putting too much heat into the surrounding metal. I use pieces of plywood clamped on with C clamps as a guide. That way the cut ends up being relatively precise and little grinding is required before the new edge can be welded on.
If you don't have access to a plasma cutter, I'd try to use the grinder cutting wheel first. Sometimes it just takes forever, depending on how it's welded on. Like the plasma cutter method, using a grinding wheel to remove leaves little grinding work to do before the new edge can be welded on. It's a fairly easy job that you can later be proud to say you did yourself. Good luck!
