Using UDK isn't the best way to learn programming, it is good for artists and game designers, but programmers, even if modding udk, should start at the basics. You are only 18 years old, so if you like to be a coder for a big studio you should start with a degree.

An other thought about UDK: studios don't need coders to use the UDK, that will be handled by game designers/artists, they need coders to do the things which are not supported by udk out of the box.

Using UDK isn't the best way to learn programming, it is good for artists and game designers, but programmers, even if modding udk, should start at the basics. You are only 18 years old, so if you like to be a coder for a big studio you should start with a degree.