I'm interested in learning how to create maps for UT3.

Based on how maps were created in other UT games, how long would it take to say, build a basic map with two levels (upstairs and downstairs)?

IS it possible to just edit an existing map and move everything around?

Do you have any excellent map tutorials to the existing UT games?

I'm just curious about how long this process would take as I have some pretty good ideas on how I want a level to look.

For the record I can do programming in stuff like VB.NET, Java etc.