The oil cooler isn't going to give you more power or make you faster in the same way that dropping in a cam or putting on aftermarket exhaust will, but it can help in a way. When an engine gets too far past it's normal operating temperature the power is going to start dropping off slightly, the oil cooler can assist in keeping it from getting that hot that it starts to lose efficiency. Another bonus, and my main reason for adding the oil cooler, is that it can help with clutch dragging problems. Most warriors have a tendency to start dragging when they get hot, which makes it difficult to find neutral or get it back out of reverse. This happens because the heat will cause the metals and clutch plates to expand which will create excessive friction between them. Cool oil = cooler clutch parts = less dragging.
I think Dean is thinking about some other shock, the stock front shocks do not have any compression nuts holding the spring in. You might be able to remove the spring by compressing it and sliding out the upper retainer from the shaft, I can't remember if the retainer is slotted to do this though, it's been a while since I've had my warrior. Most likely the colors you're seeing are just the different model years changing. Through all the years I bet there's 20 different color combinations for the warrior.
The fenders are a personal preference thing, I don't know what kind of answer you're looking for here, some of us like it and some of us don't. When done right I think cut fenders can look good, sometimes it doesn't look right but some of them look badass that way. Deathshadow's quad looked beastly with the all black fenders and the cut he did, YeOldeTyme's warrior also looked damn good with the cut fenders. I didn't do it myself because I liked the way mine looked with the full fenders, and I end up in the mud a lot so the fenders offer some protection to keep your nostrils from getting plugged up with dirt. I've heard arguments that cut fenders help the quad fly better off jumps because the big stock fenders sort of act as a spoiler and will push the front down and can catch the wind on a rainy day. I don't know if there's much truth behind that or not.