As to the other, it turns out that the phrase, "Fits most rotary lawnmowers," actually means, "Remember that twenty bucks you spent last summer? Kiss it goodbye." There is no way to attach the "universal" de-thatching blade safely to my fairly standard Craftsman mower. Rats.
My disappointment at that was tempered by the fact that my daffodils are blooming, and the tulips are getting close. Spring is here.