There isn't much to know, just run the update. It should preserve your text messages, contacts, etc. You may lose calendar events (I did when I updated with the generic firmware), but if you use Google syncing, then it will re-sync the events. There's very little to worry about.

Having said that, after an update I recommend a factory reset to clear the cache and settings. The reset will wipe the text messages, phone contacts, calendar, downloaded apps, everything (the memory card will not be erased though). It will even run the intial setup again just like when it was brand new. This sounds like a hassle, and it is a bit, but it does ensure the phone is starting fresh without any old data corruption. You can get a backup app to save settings, texts, etc.