1. Some AR parts will work, alot won't. There are no suppliers for parts. You see them once in a while, but not often. You can modify still more AR parts to fit, but still there are plenty of parts that are Daewoo specific and will require custom fab.
2.Yes, you can use an ACE stock kit. It's a high quality part, fits well, and you use US made internals and a USGI mag for the parts count to get the pistol grip. I don't have the URL, but I'll see if I can find it.
3. Accuracy is as good or better than an AR. Reliability is better. It's far easier to clean and maintain. It's still just as light as an AR too.
I own a Pre-ban K2, and it would be the perfect weapon for anything an AR would do. There is not the parts availablity, nor the wide variety of variants available as an AR. If you just want a good serviceable rifle, they're hard to beat. If you're into all sorts of conversions, or different uppers, or stocking every extra part, then you're out of luck.
Most of the lower parts and springs are AR interchangable. Some fitting may be required. The firing pin is not AR, and is longer, so you can't modify one. The bolt carrier can be made from an AR unit, but that's alot of machine work. The bolt is close to an AR but not close enough. The ejector would have to be custom. Gas system parts and really the rest of the gun are pretty much Daewoo specific. Some of the sight parts (like the windages drum) will interchange with the AR. Little stuff like pins and springs are mostly AR. You can pretty much cover most of your probable weakspots with AR parts or AR modified parts. The firing pin and bolt though are pretty key, and you'd have to get the real thing or custom make them.
I really like mine, and I'd buy another if I had the money kicking around and nothing else to buy. I would buy a Daewoo over many other rifles.
Ross