This installment of "Adventure Notebook" is a bit higher-level than previous notebooks, and it includes a monster that does not exist in any monster manual, as far as I know--vampiric duergar. Coming up with stats for them is your job. My suggestion is to double their hit dice and give them most of the vampire's special abilities (your choice), but you might want to present them completely differently.
This location would work well tacked onto a larger dungeon. Butt it up to any unexplored door and it's ready to go.