Everyone has covered the important stuff. Gloves, glasses, etc are a must. Cover vents and honestly laying an old sheet down over the dash is a good idea. After trimming the old sealant it is a good idea to put some primer or touch up paint down over any bare metal where the pain may have been scraped off. These areas can rust and get bad before you ever see them again. I prefer 3M WindowWeld for sealant on the new glass. Window sealant is messy! I use 3M acrysol to clean it up, but I believe rubbing alcohol and similar chemicals work as well. They just may not be as fast.
Keeping it inside out of rain is excellent advice and I might avoid washing for a few days.
Having a friend help with the install will make it much easier. Just make sure this friend is not a clutz and is a bit careful. You don't want to break the new glass.
