Stinker from Space by Pamela Service

Tsynq Yr, a Sylon scout and pilot, is flying a stolen spaceship behind the enemy lines of the Zarnk Empire. In the course of evading a Zarnk battleship, the Sylon crash-lands his vessel on Earth. Grave injuries force him to abandon his body and assume the form of the only available host -- a skunk!
The alien's luck improves when he chances to meet Karen, a girl who dreams of space adventure. Thanks to his powers of telepathy, he can communicate with his new ally, who gives him the all-too-fitting nickname Stinker. Although he finds Earth technology primitive, Stinker is helpless to return to Sylon with crucial information for the battle against the Zarnk. Karen enlists her computer-savvy classmate, Jonathan, in carrying out an ambitious plan to "borrow" a space shuttle. In the meantime, the three must avoid drawing the attention of their families, NASA, and the Zarnk as well as the local skunk population. This thrilling escapade will enchant young science-fiction fans.