Don’t think there really is a website that helps out with all the different types of games but you can get a few good video tutorials on how to create maps on Hammer (source engine games). Do a little Google on “hammer video tutorials”, but anyway more to the point. I would have gladly accepted your help though I think your map is a little too simple and normally tend to work on larger and more diverse ideas.
But after my experience with the Battlefield Vietnam tool it is a very good and simple tool for creating maps, though you better get to know 3DSMax very well because you will be using that a fair bit.
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