[Phil Masters]

Yeah, if you just want a somewhat WH-ish feel to the game, low-starting-points characters, bad German, and a lot of grubby sordidness in the setting furniture should do it fine. If you want specifics like gunpowder, systematically dangerous magic, and (supernatural) corruption, you'll need to add some stuff from the main GURPS line.

(I'd probably suggest, minimally, acquiring GURPS Low-Tech for some equipment including firearms, and GURPS Thaumatology to skim for ideas on ways to add messiness to the magic. Other things would also help, but that's your keep-it-simple starting option.)