So I finally got around to ripping the audio from an ISO, and it turns out it's simply uncompressed PCM files. Import as raw data with Audacity, problem solved. Except the files don't loop obviously.

Now I suppose I could just manually cut and paste after trying to find the loop points/samples, but I thought I might as well go ahead and ask if anyone here knows of an easier/faster/more preferred method of doing this?

I know for the .vgm files at project2612 they do the same thing, then (I believe) run it through a .vgm editor tool that performs the looping.

Not that it matters, but the game is Yu-Gi-Oh Duelists Of The Roses, currently only ripped as 128kbps mp3's around here.

There's either that or copying the track twice into an audio editor and crossfading them at the loop point, which is what I do and tends to be easier. You're prone to get a click if you copy and paste into the track and don't get it absolutely perfect. You certainly can get completely transparent results by crossfading, but even that can take some work. I don't think there are any other ways to do it though.

Yeah, click results because the track cut offs to nothing rather than fading, so trying to join them that way is practical suicide. On a whim, I tried to see if foobar could read them, turns out it can, and loops them correctly. Problem solved.

Just for my own knowledge however, how does crossfading work?

Basically, doesn't it simply involve fading out on one track, and fading in on another at the same time?
If you have them aligned precisely, sample to sample, then it should sound very smooth, because, if you imagine a single track having no volume changes, then the entire track will be constantly 100% volume... not specifically 100%, but relative to the current volume.
Then imagine a copy of that track, but the first track fades out, you'd get a volume of 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10% and then 0%.
Then the second track would fade in, and the volume would go 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70% 80%, 90%, 100%. If you have 2 tracks playing at the same time, their amplitudes are added, right? So the 100% - 0% fade out, adding to the 0% - 100% fade in will mean that, for example, at the start of the fade out/fade in, you'd get 100 + 0 = 100, then 90 + 10 = 100, then 80 + 20 = 100, etc, and thus you'd have just 100%, i.e. there'd be no audible fade out. If for example, you converted the Cave Dungeon themes from the USF rip of Super Mario 64, if you faded out on the main version, and then faded in on the "Hazy Maze" version, what you'd hear is the slap bass melody would fade out, and the eerie humming instrument thingy would fade in, but because the rest of the song would be exactly the same, they'd just play normally.

Of course, I may be completely wrong about the entire "cross fade" thing.

That's pretty well it.