[plt-scheme] print-object equivalent

I have merrily hacking using DrScheme and wanted to know if theres
some way to define what controls the printed representation of objects
of a given class. I am looking for plt schemes equivalent to the print-
object generic function from lisp.

Also I was looking for advice to implement logging in an application
which uses objects. Is it possible using some metaclass based magic to
get all defined classes in my application to log all messages they
receive ?

PS: Thanks for the great *searchable* documentation that comes with
DrScheme. It makes DrScheme one of the most productive environments
ive used in a long time.