To install the blue head style ceramic rotary valve seal does require some machining. I had mine done a few years back when I had my grey head overhauled prior to first flight. I don't have an exact cost because it was included in the complete overhaul invoice. Any of the rotax repair centers should be able to quote a price for this.

Others have reported that this upgrade isn't necessary if care has been taken to run dex cool (silicate free anti-freeze) with distilled water. Telltale signs of leakage would be a milky appearance of the oil in the rotary valve reservoir.