I converted one of the regular DCC modules on the fly, and that was easy. Mostly it is a matter of scale (and if you are familiar with 3rd edition, it will help) and tone, as D&D 5th in my view is very heroic and high powered in a style, that neither DCC or Lankhmar is.
As such I would say, that the adventures can be converted on the fly, if you play loosely with the system as my groups does. However, you might want to put in some restrictions regarding choice of races and classes, if you will play the adventures in the Lankhmar style.
I would also recommend getting the campaign box from the previous kickstarter - and if I may, I would actually suggest playing with the DCC rules, as they are very easy to learn for D&D players and quite a fun alternative.