Hi M. R.
Welcome to the Support Communities!
There are a number of ways to changle the preferences in Mountain Lion so that text and icons are larger.
The first way would be to change the display resolution.
This article will explain how to change settings in System Preferences.
You can adjust icon size and other settings in Finder:
You can also adjust the settings for the applications you use the most by choosing Preferences from the main application menu. Ex. iTunes > Preferences > General - "Use Large Text For List Windows"
Most appliations also have a View command on the menu bar that will allow you to change settings as well.
View > Show View Options
I hope this information helps ....
Have a great day!