harbor frieght is great for deals, but not sure if i'd get a torque wrench from them....
As stated, I'd go with craftsman, kobalt, or husky... they are all pretty much the same quality and price and all have warranties. Not sure what the TW warranty is since its not a standard wrench, so make sure you get the details if that concerns you. I would be surprised if, like paxx said, they are warrantied for lifetime since they require adjustments and calibration. I would think they would be warrantied more like power tools.
I don't know if husky and kobalt have instore exchange like craftsman does either...
Snap-On will be of high quality, but you're gonna pay a pretty penny for it. It will also have some kind of warranty on it.
All the warranty info is available online at the respective sites.
I'd also just get a 3/8 wrench. No need for the 1/2. Most bolts that would be of concern for you can be handled with a 3/8 wrench. Hell, I don't have one, nor do most people, so I just bolted down my manifold with a standard ratchet.