Did this myself a week ago. You don't need to drain/remove the radiator. One hose is a little in the way of the top bolt for the battery shelf but it's easily bypassed. Removing the radiator would make it easier to reach the front header, but in my opinion it's not worth the extra time and headache. The front header is actually easier to remove than the rear.
If you decide to remove the radiator, go ahead and refresh the fluid. Might as well since you've got it out. And you're more likely to contaminate the fluid if you drain/reuse it vice new fluid. But again, I recommend you don't bother with it, not necessary.
The only ABSOLUTE MUST HAVE is the shaved wrench. Normal wrenches won't even reach half the nuts and you'll round them trying to force it. Use an older wrench or buy a cheap one, then grind it way down. You'll still have to turn most nuts about 1/8 of a turn at a time but it'll be way faster and easier if you're not fighting to get your wrench on there too.
+1 on rpm429's comment about anitseize. It'll make getting them on easier as well as off later on. You can get by without it, but I recommend you use it.
And lastly, be patient. It will take time mostly because of the 1/8 turns I mentioned. That's just how it is. Not hard at all (with the shaved wrench), just tedious.