Do you know for sure that they have them on the floor at Anniston? I have been to the North Store a couple of times, and they didn't have any either time I went. It may be worth looking at the South Store sub forum over on the CMP forums for recent reports.
However, 8 hours of driving and gas (with gas prices the way they are) is a huge negative for me.
Add tax money if you want to walk out the door with it. It is cheaper in Ohio at least to have the rifle you picked out mailed to you.
And would it be considered a pretty fair bet that if I order through the mail that they won't be hunks of junk?
I'd bet they won't be "hunks of junk". Most people are very happy with the rifles they get. Some are not - it happens. But, they will meet, or exceed the descriptions. So basically, don't have hopes of a pristine, correct except for the trigger group rifle, with uncut oprods and a beautiful wartime stock.
Will I be happy with what I get?
I don't know, will you? You will get rifles that meet, or exceed, the grade descriptions. If you don't want to run the risk of getting one that barely meets SG criteria, get a higher grade. That being said, most rifles do seem to be better than the descriptions. They will function. If there are any problems, the CMP will take care of you. They have great CS.
Or do they just randomly select rifles from a crate and send them over?
Yeah, basically, you will get the first SG they grab.
And can you request anything when you order?
Yes, but of course, you may not get it. When I ordered my carbine, I requested one with wood that was hand finished with unicorn blood, and had "AM, B co, 15 In, 3ID" carved into it - but sadly I didn't get that.
If you keep your request specific, and basic, the higher the likelihood that it will be fulfilled. If you want a WW2 SN, ask for that specific range of SNs. If you want post war, ask for that range. (I've read repeatedly that the packers may not know what range of SN is wartime etc, so list those specific numbers.) If you want a GI stock, ask for it.