Doing a 520 conversion isn't hard, but it helps a lot to know a few of the tricks and tips. Having the OEM shop manual handy is always a good idea.
I'm actually in the process of writing another one of our "How to" articles to add to our collection of maintenance articles on the Turn One Racing website, but since it isn't finished yet, so I'll throw a couple of things out there for you.
First of all, you need to start with quality components, which of course, I prefer to get from Turn One Racing http://www.turnoneracing.com/Chains-and-Sprockets-c32/
But I'm kind of particular that way :-)
If you have access to an impact gun, that makes the whole job a lot easier, not to mention faster. If you don't, that's okay, just be prepared to need a friend to help steady the bike and/or stand on the rear brake while you remove and replace the front sprocket.
You can break the chain with the chain breaker tool, but it comes off faster and easier with a grinder, or even a Dremel with a cut off wheel. Make sure to wear safety glasses for this part.
If you don't have an impact gun and access to an air compressor, don't cut the chain until you've loosened the front sprocket nut, because you'll need the chain on the sprocket to hold it tight while you break the front sprocket nut loose.
And if you don't have an impact gun, you'll need a long breaker bar to loosen the front sprocket nut, you may also need a friend to steady the bike so it doesn't fall over while you crank on the nut.
Also, a 2x4 in the rear wheel between the swingarm/rear stand and the wheel arm to keep the wheel from moving past the swingarm will help lock everything in place while you lean on the breaker bar.
Once you get the front sprocket loose, you can cut the chain and pull the rear sprocket as well.
While measuring your chain, consider where you want the wheel to sit with your new gearing. The longer the wheelbase the more stable the bike will be, but keep in mind the chain will stretch a little as it breaks in.
If you're not going to be changing sprockets back and forth for different situations, then just set the length in the middle of the range and stick with it.
Double check the chain length before you mount it, it's the old "Measure twice, cut once"
Make sure you properly tourque all your sprocket nuts, and set your chain tension, being careful to keep the rear wheel in line.
Pump your rear brake before you ride, and best of luck!