And I'll be buying used cars, but if they're from dealerships, does that mean that they've gone through some sort of minimal servicing? Are dealers, at these dealer-only auctions, buying these cars blind?
I believe they do some sort of inspection at auctions and allow you to return them if you take them back to your shop there is some sort of major unlisted defect but that only works well for an actual dealer. If you are buying from an actual dealer and not an auction always get your car inspected. Dealers are no more trustworthy than a random dude on Craigslist and that 100 bucks can easily be negotiated off based on what your independent mechanic finds.
Every car auction I have been to is a "bought as-is" deal. Period. No returns for any reason, whatsoever. You bought it, get it off our lot in the next 4 hours or it gets towed and you pay the fees. Dealers aren't much better. They just get cars, shine up the outside, and put them on the lot. Used cars at dealers don't necessarily get any sort of inspection. (And what kind of inspection could your average Ford dealer give a Nissan Juke - for example - anyway?) The only way to buy a used car is to know something about it. I suggest finding a common car - an Acura Integra, or Ford Taurus, or whatever - and learn basically what goes wrong on them, and what to look for. Then go look at 10 of them. Check out the things you know how to check, and then - if they pass that cursory look - take them to a dealer and pay the $250 for them to do a pre-purchase inspection. Then you will know EVERYTHING wrong with the car, and be in a better position to haggle. (Of course, a lot of sellers don't let you do that any more. You pay cash now, or you go away.)