Do you need Magma?  I've not tried installing the Magma-Pier integration, yet (quite frankly, Keith's instructions are a bit vague and needs a bit more detail for a newbie like me), but the experience of just installing Pier is fairly straightforward (unless something has changed since my last install).  Just install Pier from SqueakMap, and it'll take care of all the dependencies.

Even when installing via the Monticello repository according to the instructions worked painlessly.

Try the instructions here for the installation without Magma:
http://smallwiki.unibe.ch/smallwiki/pier/installationofpier/

If you're determined to get Magma running with Pier, you might want to try getting help on Magma's mailing list, since it seems that most of your problems come from Magma.

Magma List: magma@lists.squeakfoundation.org
Magma List Archive: http://lists.squeakfoundation.org/mailman/listinfo/magma

I feel similarly in regards to SqueakMap.  It seems to lack automatic dependency resolution, and puts all the dependency resolution in the hands of the package developer, of which many pass that burden on to the user.  The most well-behaved SqueakMap package so far for me, is Pier.  I can take a fresh 3.8 image and install Pier, and it'll install all the other packages that it depends on, plus setting things up so it can start running once the installation is done.

I always keep a fresh image that I can restart on.  Many times installing packages from SqueakMap and fiddling around Squeak can break my image or change file, and I don't know how to fix it, so I just start fresh again.

-Bill