Classic fool who has default Full Backup model and out-of-control log file ---- how to I get this controlled?
Do I have to do anything OTHER than a switch to the simple recovery model?

If you have a full backup, and don't need point-in-time recovery, simply switch the database to Simple recovery.  After the next Checkpoint you should be able to shrink the log file.  If the active VLF happens to be at the end of the file, rebuild an index or two, and try again.