So I saw this and the sick twisted part of my mind kicked into gear....
 

http://fortwayne.craigslist.org/pts/5175837039.html

For my 2005. Think it'll work? The guy wants too much I think...

Not sure what they cost new. Looks like he has everything there.

So here are my questions about this:

It's off of an older car, I am guessing a Supercoupe. Can you rebuild these things? How complicated would installing it be? What kind of power might I expect? Will I have to get a special tune for my computer? The idea keeps growing on me and it seems like something I might like to do, but there are a LOT of if's here...

I could be wrong if so someone will correct me, but I don't think as is it will fit, as it looks to be for the 3.8, so the manifold will be totally different, and most of the other parts won't work either.
Just stick with the plan to sell your six, and try to pick up a decent first gen.

Also it might cost, but instead of just craigslist, list it with a nationwide seller, someone will want your car, it is very clean, and tastefully done, maybe even list it a little higher than you have it.

Are we talking like Autotrader?

Yea something like that, if it was me I would do a little research, as I've heard one of them cost's about $200, but keeps the vehicle listed till sold.
Like I said do some research and find one you like, there seems to be quite a few.
car sales websites

Yeah, I kind of get tied in knots if I'm not doing something with the cars. :)

That is off a 3.8, single port V6 and no it will not fit on your 4.0. Sorry.

Matthew