Wow, timely subject to me. My GM1060E has one season of mowing on it - I bought 3 spares at the end of last season, with the plan to pull and change them out. Well the anxiety monster got me on it, and had not done it yet. I even already have mowed once. This thread tells me I was right to fear it being a pain. My manual does not mention what direction thread. It does mention that the blades spin counter clockwise looking at them from the bottom. And the blades were more in the area of 75.00 for all 3 (from JD dealer). Bush hog blades are entirely different from the grooming mowers. I could try to find my order and get the blade # from that.
I recall when I bought my set up, one dealer inferred phase out of Frontier. I really think it was a margin thing and they wanted to sell something else with more profit - same dealer would only give very small discount on quote.
I am still trying too figure if the gear box oil is checked and filled from the breather port - the only thing I can see. No detail on how to check or fill in the manual. It does say 103 ft lb for blade torque though.