It's not. I used to teach it.
It's basic modules - one in foundation of pc's, other in knowing your computer, then powerpoint, excel, word, Internet and Access.
You can go to any centre that does the testing and ask to do just the tests but as many are government funded they will want you to do the whole course.
If you wanted to do it in one go, the course and one exam a day would take you around a week and depending on your circumstances cost you anything from nothing to £100. TBH you wouldn't even get confirmation within that time.
On the whole though, although the concepts are easy for anyone who knows about computers, there are several tricky questions in there that I have seen engineers fail on (because they just don't have to talk about what a monitor size is in centimetres in real life
or similar). Passmark is around 75/80%. Personally I'd not lie about it cos it's not a great idea to get off on the wrong foot, and if they do check it up you'll be out on your ear.
Tell them that you've taken advice on this and that the ECDL is actually for those with less computer knowledge than you, but you'd be happy to do it if they want you to. That way they'd probably pay for it too!