Not a flame, but just don't want to see people waste their money.
Now, for what you are wanting, it does seem it would be more cost effective to sell your present car and use the money to buy one with a V-6 and MTX. When you say you owe too much to sell it, are you saying you owe more than it's worth? If so, that really sucks, but I don't know if that will ever go away. Undoubtedly, though, you will get more for the car selling it privately than trading it in to a dealer, and perhaps more now than later, and certainly more now than you would after modding it.
If you wanted to go the 3.0 route, well, that's something you can't get with a chassis trade, so it might be worth it.
Otherwise, if you are really that strapped for cash--and this can be an expensive business--I really would spend some time in the Zetec forum and see what's out there. (A lot more, thanks to the Focus, esp. the SVT). I drove a car with the Zetec once, and I expected a huge difference from my V-6. Instead, I found the car willing and quite fun.
