Yep, the guard will allow a bit more air to the face of the radiator, but it has nowhere to go in the engine. This leads to more air being splashed over the sides and top of the car as opposed to through the radiator. Taking it off will help extend the life of your other components (those not designed to sit in a 200 degree oven..., CV's, mounts, timing belt, ect.)). 16k is a lot for repairs thus far, and 30k outta your tires is also really crappy. I wonder if there was more to his driving then getting from here to there.. I know the 6-cyls are bad at being hot, but most of the 5's are pretty good. Then again, I'm not in texas..

If I were you, I'd leave it off. Most of the impacts you'll get underside is from rocks bouncing from either cars coming the opposite way, or those in front of you. There is the occasional tire/debris on the road to watch out for too. The easiest way to get around it is just defensive driving. Leave lots of room between yourself and the car in front of you.

As far as the handling part goes, if you haven't really used the car before (like taking butterfly off-ramps at highway speeds...) you won't notice it. Its a small change between the two, but it'll be consistent. Its more of a problem if you were taking the car out on track days, took it off, and kept pushing the car to previous limits.

As to economy, if it drops you 1% (which I think is high) it'd be ~.2mpg difference. Not that noticeable.
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If you're not driving it "like its stolen," are you really driving?