Easy, with a bit of patience.
If you need to cut the stays, I'd recommend putting them in a vice to hold them steady while you hit them with a hacksaw - or just use a cutting disc on a dremel.
I did it myself. You'll need a saw to cut the stays to size and a fair amount of fettling to get them right. Mine snapped off a few months later so I'd managed to balls up the installation somehow. If I could go back I'd have asked my LBS to install the bloody things.
Fitting blumels - how difficult? Never fitted guards before. Can I do it myself at home?