I'm confident that I do not need a password for my computer. How do I remove passwords for things like when the screensaver activates and installing software?
While this statement is a general attitude that I dont agree with, in the spirit of answering your question, I'll continue without further biased objectification.
There are a few areas of the system that you can utilize to process this request. First being the "Screensaver Password" that you mention. Go to System > Preferences > Screensaver In there, you need to disable the checkbox titled "ALock screen when screensaver is active"
On the login screen you can set an auto-login to a user. System > Preferences > Login (this may be system > administration > login.. please verify as I'm not in-front of my Linux PC) you can then set the system to auto-login a given user.
However please note that after you have logged in, if you have stored passwords in your couchdb it will prompt you to enter your password to unlock the keyring so your wifi can auto connect (as an example)
Regarding your software installation password, there is no way to default this that I'm aware of, as sudo will ask you for a password. This security model is enabled so you have to think about what you're doing before you make system-wide changes such as installing software.
Please see: this link. it will help to explain why the current security model should be the default.
"Nobody will ever compromise my computer." falls under the category of Famous Last Words. Reconsider.
That said: for the screensaver, go into the screensaver preferences and uncheck the option to ask for password. For administrative tasks,
There's a multitude of reasons why having password protection on sudo actions, or login, but if you really need to not do this you can do it like this:
Find the line with your username and change it to the following:
That should give you the results you require...