I did this yesterday. Comments:

1. Ian's unix squeak website works very well. The only thing I missed was
  a link to the debian packages.

2. I tracked down the readme that describes the debian apt source entries.
The deb-src entry causes apt-get update to give me a "Bizarre Error", I
don't know why. I commented it out. Ie,

deb-src ftp://st.cs.uiuc.edu/pub/Smalltalk/Squeak/3.2/unix-linux/debian/ unstable non-US
...
Get:2 ftp://st.cs.uiuc.edu unstable/non-US Sources [482B]
99% [2 Sources gzip 0] [Query]
gzip: stdin: unexpected end of file
Err ftp://st.cs.uiuc.edu unstable/non-US Sources
  Sub-process gzip returned an error code (1)
...
Building Dependency Tree... Done
W: Bizarre Error - File size is not what the server reported 0 482

3. The debian binary packages don't include SqueakV3.sources so I had to
install that manually. Maybe that was due to 2.

-Simon