Aliya Summary: The total for the Gershon family: 2,630. The Merari family: 3,200. Thus the grand total of Levites eligible to transport the Tabernacle and its vessels: 8,580.
Rashi says the Avodat Avoda (kind of a strange phrase) refers to playing musical instruments. As far as Avodat Masa is concerned – the Gemara in Chulin comments that only when there is heavy manual labor involved, then there is an age limit for the Levites.