Have the villain as some crafty, sly and very, erm, elegant (sort of like Hanz Gruber from Die Hard). (Just an idea for a villain, start with a simple idea. Craft the actual character after you have an idea of the setting and any details you want)
My suggestion, start small. Don't overdo yourself with a large-scale project. Start with a short story and just try and find the niche you feel comfortable with. Experiment with characters, settings, dialogue and speech patterns. Work on your details until you feel happy about it. And most of all, don't let ANYBODY tell you how it has to be. It's your book, and writing is first and foremost (well, it SHOULD be anyways) for yourself. Like my Creative Writing/English teacher says, "Write to oblivion. If anyone else likes it, then that's just a bonus."
Once you feel comfortable and find how you like to write it, then move on.
Also, don't let the details pointing it out to be steampunk become side-notes. Make them prominent, so it doesn't feel like it could be anywhere in any general style.