Great stuff, I am glad you got it working ok!
Question 1 Parts cost Very little! However I over-ordered all the components, from Mouser in the us, i.e. needed 2 ordered 10 etc,
0.1u 16v £0.034 10 off
0.01u 16v £0.069 10 off
1u 10V £0.346 5 off
603 ferrite £0.076 10 off
Connector £0.809 2 off
You definitely NEED the proper tools. It is not impossible to solder these little components with the right tools, especially a magnifier, but it is hard.
The MAJOR problem is cleaning the lumps of solder off the vacant pads, without removing the pads by accident. On the 4 caps in the pi filter, one end of the caps is the 0v ground plane. This sucks all the heat out of your dewicking braid and soldering iron. I have a 90w rework iron with a 0.2mm radius tip, it struggles to get the heat into the braid.
Here is the URL of a video showing soldering of 0402 components:- www.youtube.com/watch?v=66GV4OuShzI
When you look at the video, remember the pads in this video are CLEAN with no great lumps of solder! When GlobalScale manufactured the Plug boards they used a "common" mask, so all the unused pads were covered with solder paste, so when the board went through the oven, the paste fused into lumps on the unused pads. It is hard to balance a component on two solder mountains!
The connector is easy to solder.
I have no idea who or how much they would charge to solder 8 0402 caps, one 0603 ferrite and one connector.
So you see not a lot, What was expensive was the Fedex charge from the states, (I could not find the connector in the UK) I think the carriage was £12.00
Question 2 Port multiplier Don't know, haven't tried one, I don't see why not, its a standard sata port, SATA 2 with bags of bandwidth, if you have one lend it me and I will try it !
Question 3 Have you looked at www.openrd.org?
You can get the specifications there. There seems to be a preference for OpenRd-client units, NEW IT is selling them in the uk at the moment.
A really think that it will not be long now before we can buy a version of the Sheevaplug with E-Sata as standard.
see the post:- http://plugcomputer.org/plugforum/index.php?topic=1046.0