I also have a new MX5060, though I have never had to change the belt. I don't believe that you have to "line up" the blades in any special order. The manual doesn't mention anything about it. Looking at the deck, I don't see anything that would keep the blades timed or synchronized. The easy way to tell is to turn adjacent blades together to see if they touch. If not, just put on the belt and start mowing...:smile:
By the way, how do you like the mower? I've only used mine for 12 hours and I absolutely love it!
Bruce