“"Woo-hoo!" … as suggested by the starts of 17-, 24-, 39- and 49-Across”

Undergoes a chemical change

Yosemite or Yellowstone

Hairstyling stuff

Send out of the country, as goods

One of many in an autumn pile

Alter ___ (secondary identity)

Rap songs and such

Certain endurance race, in brief

Bowling venue