Can't help you much with the first question (go for what you want!), but a comment or two on fleet cars:
I have been lucky enough to have had a number of fleet cars over the past 10 years, and in fact I bought 2 of them from my employer once they were turned over. Most respectable fleet companies are pretty OCD about maintenance and repair, so its unlikely you'll find one that was trashed and dumped - the fleet companies won't allow it. Remember, corporate fleet vehicles are not owned by the driver, but by the employer and the leasing company.
As to low mileage, its is up to the fleet program manager when to turn in a vehicle. The ones I was in were pretty high mileage ones - I would do upwards of 40+K a year and they turned the cars over at 65K miles, or 3 years. Of course there are other programs (like executive drive programs) that turn cars over very quickly, as you have found.
Personally, I wouldn't let the fact they were fleet get in the way, unless I found out the fleet was a "rental" fleet....then I would probably stay away!