If you really want a good intro to Spalding's early life, read Sex and Death to Age 14...
Spalding started in acting in experimental theatre in NYC and is most famous as a founder of the Wooster Group. His early films were terrible adult porno flicks, but he graduated to small roles in films (to keep his union health insurance). He evolved on stage by inventing or perhaps reinventing the monologue. He performed these intensely personal, hilarious monologues world wide and 3 were made into films - Swimming to Cambodia, Gray's Anatomy and Monster in a Box. Terrors of Pleasure was a HBO special.
In 2001, his life took a sudden turn as he suffered a head injury in a car accident in Ireland. Perhaps this brought out the true neurotic/obsessive, bipolar character that he played so well.
In January, 2004, Spud went missing and was suspected to have jumped off the Staten Island Ferry. On March 8, 2004, his body was discovered and we lost a truly wonderful author, actor and person.