I've made some custom gauge legends and I needed to get the speedo needle off too, but being a chicken, I got a pair of long nosed pliers and held the shaft behind the speedo face and just pulled the needle off with my fingers - I took one look at the tiny bearing on the needle shaft and didn't dare risk pulling it off without something behind the dial...
I'll post some pics of my new gauges when I can get a decent night-time photo...