[plt-scheme] Incremental development with DrScheme or MzScheme

Howdy,
I would like to start a long running process and then redefine parts
of the Scheme code, recompile, and have the long running process pick
up these changes.

My understanding is that DrScheme Run button cleans out the
environment for the "Definitions" and "Interactions" windows. Is this
correct? Clicking 'Run', I see it kill my running GUI and start a
fresh copy.

Should I use (load "foo.scm") from the interactions window to reload
changed code? For partial load/compilation just copy and past s-exp
that I want to re execute?

I am looking for something like SLIME+sbcl where I can compile an
s-exp and this immediately shows up in the running environment. If
this isn't possible, then a pointer to good workflow for DrScheme.
Thanks.

Congratulations on an excellent project.

-- 
Thanks,
Austin King