How do I tell valgrind to memcheck forked processes?

I have a process x that I want to check for leaks with valgrind. The problem is that x is run by y, and y in turn is run by z. I can't run x standalone because y and z setup the environment for x, such as environment variables, command line switches, files needed by x etc.

1. Is there any way I can tell valgrind to run on z but to follow any forks it finds and report them too?
2. Is there any way I can tell valgrind to follow any forks but only report on the process named x?
3. Is there any way I can tell valgrind to attach to already-running process, the way I can do with gdb?

I don't know if this matters, but I'm running under SuSE64 linux and valgrind-2.4.0.

Thanks!