How do I regenerate a map?

This isn't a request forum so it is beyond reasonable expectation for any of us to write the script for you - that said, we'll do what we can to help you on your way.

An important method that you'll want to be familiar with is Clone(), read about it here:

http://wiki.roblox.com/index.php?title=Clone_(Function)

I haven't done this before either, but it really shouldn't be that difficult as long as you're aware of the above function. Make a copy of your map from wherever it is stored (Lighting, ServerStorage, etc...), then whenever you want to 'regenerate' the map just delete the copied version and make a new copy from the storage location.

Something along the lines of:

currentMap = nil
function Regenerate()
    if currentMap then currentMap:destroy() end
    currentMap = game.ServerStorage.YourMap:clone()
    currentMap.Parent = workspace
end
Regenerate()

Hope that helps!