Conversation so far:
what did casey do in early career?
he spent time in Detroit as a disc jockey for radio station WJBK-AM (and doing such shows as The Lone Ranger and Sergeant Preston of the Yukon).
how long did he stay there?
CANNOTANSWER.

Question: what did he do next?
Self-contained rewrite: what did Casey Kasem do next being a disc jockey for radio station WJBK-AM in Detroit?