Want to take a 4 or 5 day escorted tour of the area. Do not want to begin in Paris. Would like to stay in one of cities in the area, then begin the tour. Or need a name of a company that will plan day trips in the area. Need name of a good 4 or 5 stay hotel or Inn in loire valley to be based.
Why do you want to take an escorted tour? Just rent a car and drive yourself! The Loire is so gorgeous with vineyards, cute towns, and lovely castles everywhere. Last time we stayed at Chateau d'Artigny which is cool to be staying at a mini-castle yourself. It's also centrally located. You can check out http://www.grandesetapes.com/en/ for other castles and grand mansions in the area (and all over France) to stay at, some of them not much more expensive than staying at a normal hotel; we used this site for both Artigny and Esclimont (even more beautiful than Artigny since it has a moat, but not central to the Loire).
Definitely visit Chenonceaux and Chambord. Amboise is a different type of castle, the fort-type (so more history) instead of the pretty castle-type, and you can see Da Vinci buried there. With a car you can just drive around and whenever you see a winery or cute town or chateau, stop by and check it out. Fontevraud Abbey, a medieval abbey complex, is also a worthwhile stop for something different.
Just get an international drivers license from AAA (though I've never had mine checked, but better safe than sorry). It's better if you know how to drive stick/manual as rental cars are cheaper, but you can get an automatic transmission too (though better pick those up at the airport). Get Tom Tom Europe for GPS as well as a couple good driving maps from Michelin (you can buy those when you get to France), and have a great adventure!