^Agreed. You need to unbolt the swingarm to get the old guide off, but its not too hard to do.
If I were you, I wouldn't use a factory replacement chain guide. TM Designworks makes a killer chain guide system for the Blaster that is SO much better than stock and won't wear out. At least nowhere near as soon as another stock replacement. If you can afford a TM guide...even just the top piece... get it and install it. You won't be sorry.