Sounds like you need to make friends with Kahuna! http://www.homebrewtalk.com/showthread.php?t=76710
He's doing similar work -- he's using a sour mash to accomplish it, but his grainbill is a good start for your project..
As to your questions...
1. Something light. Probably pils for the base malt, and not a lot of specialty grain. Wheat is used in many authentic versions. I'd guess ~60% pils, 20% malted wheat, 20% unmalted flaked wheat.
2. You can ferment it through, you can use a clean American yeast, or you could use a belgian yeast if you desire. Edit: I'm actually not sure on this step, but am doing further research. It appears that it's acceptable to ferment first with clean yeast, OR to perform spontaneous fermentation using open-air bacteria for the entire basis of your fermentation. More as I find appropriate links. Sorry for any confusion.
Edit #2: BYO has a good article on this. ( http://byo.com/feature/1230.html ) It's looking like you want to pitch your bugs immediately, without the use of a "clean" strain. You could either buy each "bug" individually, or buy a Lambic blend such as Wy 3278. Finally, you could always try open-air for your yeast source. Landhoney did this with his nearby apple orchard. ( http://www.homebrewtalk.com/showthread.php?t=43888 ) One of the local Nebraska breweries did/is doing a lambic using naturally airborne Nebraska yeast cultures.
3. I'm not sure whether you sour first, then add the fruit, or add the fruit, then sour. I'm not much help on this one. Sorry. If I had to guess, I'd say ferment the beer partially, then add the fruit to it gradually so as to not shock the yeast too much. BUT. I'm not an expert on this by any means.
Add: This ( http://www.liddil.com/beer/lambic/lamfaq.html ) also looks like a good resource. ( http://hbd.org/brewery/library/LmbicJL0696.html ) is also a killer guide. All the info you could ever want to know.