A helpful primer from a board member of the EFF about copyright issues and DMCA takeown notices. Of course all Hitler learns parodies have been removed from YouTube because they are a very bad thing and will destroy the film industry.
If you want to see an entire synopsis of the plot go here to Wikipedia. This will probably not inspire you to buy the DVD.
If you want to see a short clip that runs for about the length of a trailer and is probably a lot more entertaining than a trailer would be, you can see one here – while you still can. Strangely, I know two people that have bought the DVD based on the evidence of the trailer alone but neither ended up watching the whole film.
What was that stereotype about Germans not having a sense of humour?