Can I move the Install OS X Maverick file to the trash?

If you have already upgraded, you can delete it.

However, if you want to prevent the OS X Mavericks download each time you need to reinstall OS X, I recommend you to create a DVD or USB drive with the Mavericks installer before removing the OS X Mavericks installer. You can use DiskMaker X > http://liondiskmaker.com

Keep a backup of the file. You may need it, if you ever have to reinstall the system and are in a situation were you cannot get online to to boot into internet recovery.

First, make sure it installed. It will normally erase itself after install, so if it is still there, I'm not sure it installed.

If that is not the case, then you can delete it, but since you still have it, you might want to copy it to an external drive or USB stick to have it around if you ever need to reinstall. You won't have to download it that way.