JFP is pretty right - except that when done properly by knowledgeable people, the swap can turn out very well. The one we did for the Boxster book is fantastic - car runs super strong, is well balanced, and just passed smog a month ago! Ours was a 2000 Boxster with a 3.4L crate motor from 1999 - very few modifications needed at all (just upgrading the throttle body on the engine to electric from cable-driven).
As I write in my book, the 2003 chassis taking a 2007 motor is doable, but you need to update the ECU and then add some wires for the VarioCam that came out in 2007. Not as straightforward, but still manageable. See the photo from my book below.
As for what I would do? I think that you need to find an experienced shop who can sort this mess out for you and has done this swap before. Riverside may not be the best location for this. I don't think I have any specific recommendations, although Callas Rennsport is the shop that tuned our Boxster when we got everything put back together. We had to install a small resistor on MAF (if I recall correctly) because the flow from the 3.4 was different than the stock 2.7. Small things like these make a difference?
I would also consider taking it back to your garage and doing it yourself - time is on your side with that one...
Hope this helps,
-Wayne
