I second paying a printer. It sounds like you'll want to scan in and possibly vectorize your calligraphy- I know there have been threads on this in here, so perhaps you can do a search for that to get you started? As far as the debossing part itself... are you looking for letterpress? Most letterpress printers require a vectorized file, but some will take a bitmap file. Lines typically need to be .35pt minimum, something to consider with regards to your hairlines. Scanning in at a higher threshold can help this if necessary.
I know there are those DIY letterpress kits from Paper Source, etc. but my understanding is that they produce poor results. And 400 cards might be a bit much for the kit. I'll bet someone in here has tried it out- might be worth searching for threads on that, too.